Head over heels for gadgets!
When I leveled up to prestige 4 in Call of Duty 4 my friend and I sort of made a bet or rather he challenged me that I could not use the M4 Carbine (pretty much the full auto version of the M16) for the entire 55 levels. I took this challenge and completed it. Not only did I not equip the M4 as a class but even when dropped by enemies I didn't bother picking them up to use. I think what allowed me to do this was the fact that I still had access to another one of my favorite guns, the MP5. Small and quick!
I still need to go through 6 more prestige levels and within the next month, seeing as how Modern Warfare 2 comes out then!