You say Black Ops, so I would guess likely something like a Glock 17 or 26, or SIG-Sauer variety, maybe even a Beretta 92 if you're talking handguns (especially silencers). If they have assault rifles, my guess would be something more like an M4, H&K MP5, maybe an FN P90, or an AK74.
Check this out too:
Internet Movie Firearm Database
In the end ...