P90
SCAR-L CQC
M249 Para (yes, you can do this. I have)
Couple of pistols and shed load of mags.
G36K
HK 416
To be honest a lot of people will tell you that you have to have something short for CQB. Now, I'm not about to tell you that an M14 is fine (although I have seen it done and an M16) but anything as long as a standard M4 will be fine for CQB. It's not the size of your gun, it's how you use it (oo-er).