Well...more to comment on here than I can remember! Where to start?
The Steyr GB. It certainly was not a commercial success, that would seem to be true. However, it's a very well made pistol. It is rather large, but only a bit larger, I believe, than a Beretta 92. Mine has always been reliable, and accurate. The DA trigger pull is a bit heavy, but nothing horrendous. I'm not sure if they all came this way, but mine (which I purchased brand new, ordered through a dealer from Shotgun News) came with glow-in-the-dark front and rear sights. Not true night sights, no tritium...but GITD material inserted into the 3 dots on the sights. This is the first pistol of which I'm aware that came with any kind of night sight as standard. (I'm not saying it absolutely was the first...just the earliest of which *I'm* aware!)
Part of its lack-of-success *may* be attributable to the Rogak-18, which was a spectacular failure, and deservedly so, from what I've read. The Steyr GB was *not* developed from the Rogak! Rather, Steyr had designed the GB, but...I can't recall all of the details now, but Steyr had some doubts about marketing it, I believe. So, they licensed Rogak to manufacture it in the states. Rogak screwed it up, badly. So, at some point, Steyr decided to go ahead and build it. I'm sure its relationship to the Rogak didn't do it any favors in the marketplace.
The H&K P7 series. While I have no idea what the total sales numbers may have been like, or how profitable it was for H&K overall, I can't imagine calling the P7 a "failure". It's a fantastic pistol...one of the finest non-target grade 9mm pistols ever built. To demonstrate it's reliability, on many occasions I have loaded one up, inserting an empty brass case in the middle of the magazine, and then proceeded to fire it, until a "click" is heard by the striker falling on that spent cartridge. It has always completely fed and chambered the empty brass case. Hard to imagine a bullet configuration that it would not feed. Also, it will continue to function 100% without any extractor. I've not tested this personally...but I have read that it is so on many occasions. A function of its blowback (gas-retarded) design, and its fluted chamber.
As far as using lead bullets...well, I have never been interested in using lead projectiles in *any* 9mm. I mean...9mm ammo is pretty affordable in FMJ. Unless you're loading your own, and trying to save every penny that you can...I can't see why you'd prefer to shoot lead in your 9mm. But, yeah...if you do, then probably not best to have a P7. Also, since the P7 uses polygonal rifling, it should not really be using lead bullets either, just as with Glocks. I know...you *can* use lead, you just have to clean every bit of lead out of the bore, before firing jacketed bullets.
I bought 2 P7s while in Germany (an M13, and a PSP), and have acquired several more after I returned to the US. The supposed disadvantage of the sound of it decocking is, to my mind, on the same level as the "disadvantage" suffered by the M1 Garand's "pinging" en-bloc clip, that is to say...largely apocryphal. If you aren't ready to fire, there's no reason to have the pistol cocked. The cocking mechanism is so simple, straightforward, and easily accomplished...there is no advantage to walking around with the squeeze-cocker engaged. In fact, it rather negates the safety feature that it provides...as walking around with it already cocked, gives you a *very* light, short trigger pull, to fire the gun. Also, it doesn't matter if you cock it before you pull the trigger, or you pull the trigger first, and then engage the squeeze-cocker...either method will fire the gun. So, anyone complaining about the sound of cocking and decocking...is not really using the pistol properly.
Detonics Pocket 9. Really well built, fairly compact little pistol, one of the smallest of that day. Unfortunately...it's still rather chunky, for a single stack 9mm that only holds 6 rounds in its mag. And, being all stainless, it's rather heavy for its size. Also, it's a DA/SA...with an acre of over travel on the trigger. No matter how carefully I've tried to manipulate the trigger, or how long I take to line up and accomplish a shot...I can not get a decent group out of it...because of the ridiculous amount of over travel. Also, I always felt as if it was trying to twist itself out of my hand when it discharged. It torques very hard...to the right, IIRC? The sights are...interesting, and adequate. Without pulling it out of the safe right now...I "think" it has the "shadow" front sight, ala HK VP70. Also, disassembly is a huge pain in the butt. Never liked it...just never found anyone that wanted to give me anything for it. I think I even have 4 or so brand new factory spare mags.
Walther P88. I brought back a sequentially numbered pair, from Germany. Superb pistol. Excellent trigger pull, both DA & SA. Completely ambidextrous. The decocking lever is also the slide lock/release...really well designed. I think it's one of the most beautiful, finest shooting (non-target) 9mms (second perhaps only to the P7, and/or perhaps the Walther P5). Because of their value, and because my Glocks are nearly as good but much less expensive, one of my P-88s is still unfired in the box, and the other has had a sedate, gentle life...perhaps several hundred rounds through her. I say this because I have read that they aren't terribly robust, but I cannot comment on this. My biggest beef with the P-88s is that the manufacturer stamps the proof marks after the finish has been applied...and it flakes off a bit of the finish right at the stamp. Seems kinda stupid for what *was* at-that-time a $1000+ pistol. Also, FWIW...I don't care for the P-88 Compact. It has a slide-mounted decocking safety (or is it just a decocker? Not certain.) and to my mind...it's ergos are far inferior to the full-sized P-88.
Daewoo DP-51. Never owned one, never fired one. But, I sold quite a few of them when I worked at a gun shop...and people loved them. Never heard a negative comment, nothing but positive remarks. I think perhaps the fact that the company was relatively unknown in the US, and what little was known revolved around their cars (which were, perhaps...not well thought of in the US, either), and its unusual operating system...accounts for, what I assume were, sluggish sales numbers. I would buy one if given a chance at a fair price. If I recall...I think they accept S&W M.59 pattern mags? I think?
COP .357. A really interesting little gun. All stainless, so quite heavy. A very long heavy trigger pull, but as it's the only safety device, and it's obviously intended for close-range work, it's usable. Not very useful today, obviously...but quirky and interesting enough to be "cool" to own one. I've considered selling mine, as it's in excellent condition, as is the original clamshell box, and the prices seem to be steadily increasing. Oddly...these seem to be seen quite frequently in their boxes.
Iver Johnson TP-22. A decent little .22. Mine has been pretty reliable, and shoots fairly well. The finish has become...quite ugly, rather like parkerizing.
Walther TPH. I bought one of these brand new, I think it was about $275? On the second or third round of the third magazine...the gun "exploded". Luckily, no injuries. So, I picked up all the pieces I could find, took it back to the shop, and they sent it back. I believe S&W was handling the warranty claims. Anyway...the shop contacted me, and said that they (S&W? Walther? Not sure.) said it could not be repaired, and there weren't any more available, so they could not replace it. So...they very *generously* offered me $100! I was furious. After some ranting...the shop passed my sentiments along to CS. They then offered a brand new PPK (or PPK/S?) as compensation. So, I decided that having a Stainless PPK(/S?) in .32 ACP would be pretty interesting. They sent it to me...except, the box said it was a .32 ACP, but in actuality, even though the serial numbers matched, it was a .380 ACP. I was disappointed. Also, a buddy of mine who worked at that shop...advised me that the Walther PP series that they'd been selling recently, were ALL being returned for various reasons. My friend's assessment...rather than firing that pistol, and dealing with returning it when it broke, as it inevitably *would*...sell it immediately, while it's still unfired in the box. If it had actually been a .32, I think I'd have rolled the dice. But, since it wasn't really what I had wanted...I unloaded it, and made a few bucks in the process.
One that no one has mentioned (I don't think) is the Intratec Tec 22. Unfortunately...I own one. It's in very good condition, barely fired. The reason for that...it won't feed worth a damn. It seemed like an interesting idea...a high capacity, very lightweight .22 pistol that used 10/22 mags. I don't think I ever had it feed more than 5 rounds in a row, before it would jam, even though I tried dozens of different 10/22 mags. Not interesting enough to have appreciated in value...it seems quite worthless.
Then there's the Grendel P-10. I bought a brand new one, back in the day. It was very light, being one of the earlier (but, not *the* earliest, of course!) polymer framed pistols, and it *may* have been one of the first polymer framed .380s. It held 10 rounds of .380 in an internal (non-detachable...as a Broomhandle Mauser) magazine...it was loaded at the top, through the ejection port. With a small adapter, it could be loaded from an M-16 stripper clip. Its DAO trigger pull was pretty long, not *too* heavy...usable. It was accurate enough, not bad, really. The takedown was a PITA, and the owner's manual omitted some vital info concerning reassembly. The first (and only) time that I field stripped it, I broke the firing pin on reassembly. I returned it to Grendel, they repaired it (I can't recall who paid for shipping it to them?), and they included a hand written note that they slipped into the owner's manual, adding the important info that was not included in the manual. I can't find production numbers...it was only made for about 3 years (because it was replaced by the improved P-12, which had a detachable 9 round polymer mag), but seeing as it was filling a niche that no other pistol was occupying, I guess it might have actually been considered successful. I sold my Grendel when a young guy offered me what I considered to be more than it was worth, and I had been debating the idea of getting "out of" .380. Later...I found a brand new unfired nickeled P-10 for about half what I'd sold mine for, with the stripper clip adapter, which I had never even seen before.
Also...the Grendel P-30. A polymer framed .22 Magnum pistol that used a 30 round polymer magazine. These are also very lightweight, even fully loaded with 30 rounds of .22 Mag. While I've heard various people saying these were not reliable...I have a pair of them, and about 14 of the mags...and I don't believe either one has ever malfunctioned, jammed, or misfired in any way. In addition, they're extremely accurate. I don't know if they sold very well...but the 1994 AWB, which outlawed their 30 round magazines...certainly didn't help them any. These are the forerunners of the Kel-Tec PMR-30.