Sideplates yep... Not necessarily for my current guns but as replacements for the buggered up sideplates I typically find on a new acquisition. I've only once needed to replace a sideplate on one of my guns when I found the part on my Shorty45 had broken loose at the hammer pin
Other than that...
Extractor
Ejector (Newest variant)
Spare sear release lever
Spare drawbar
Trigger play springs & rivets
That's about all I can think of right now.
Cheers
Bill