If we're talking about straight up BULK, I think I have to go (and you do too!!) with the Federal value pack bulk 525 36 gr JHPs... I mean they're a great deal when they're like $20 a box of 525, they get to awesome deals at like $15 a box, and sometimes they have redonkulous buys for thousands of rounds in plastic ammo boxes and it's just great buy for great ammo.
hOWEVER, I have recently been shooting and stocking Federal AutoMatch, a 325rd box that was initially $14.49 at WalMart, now is like $15-16 a box. These are lead round nose, 40 gr, semi premium semi value rounds... I find that they are utterly reliable in both my autoloaders, my Remington 597 sporter rifle and of course my 15-22 tactical autoloader. And they shoot pretty accurately when shooting for dimes (Shooting for dimes AKA trying to make small small groups, coverable with a dime, etc) with my Savage Mark II which is redonkulous accurate.
So the Fed Bulk 525 is probably the BEST CHEAPEST.... the Fed AutoMatch is the best quality for price IMHO.... but the best of the best IMHO is CCI.
I would take CCI if I could only stock one brand of rimfire ammo- I mean what else would you need if you had limitless supply of Mini Mags? 36 gr JHP and 40 gr LRN Mini Mags will do it all and do it all perfectly. PLUS CCI Makes the Blazer 500 rd boxes and CCI Standard Velocity RN 500 rd boxes - just great great ammos. Not to mention the specialty ammos, Velocitator and Stingers etc. etc.
Oh baby I get excited when I think about stocking massive quantities of various CCI rimfire ammos.... it makes me feel so prepared, so tactical , and so nefariously accurate and reliable!!!! BWAA HAA HA HA HA!!