They are all "collectible" to someone; I have a small "collection" of shooters.
"- VOPO/Russian Capture reworks (which seem to be a growing niche)
- British Proofed guns
-Alphabet commercials in general" are all collectible areas to more than a few guys.
An unusual unit marking or scarce variation could make an otherwise "shooter" into a
collectible for me- if only for a space holder till an upgrade comes along.
JMHO.