Claymores, obviously. But I usually use claymores when I prestige, and they're pretty fun to use. Watching your enemies blow up outta nowhere makes you feel good inside.
Use C4 when you are playing Domination, it's so awesome.
Place a C4 pack at A, B, or C
Run somewhere else and when you hear that guy say,"We're losing A/B/C!!", just double tap the square button(PS3) or the X button(360) and you get 10 points or something.
depends what your doing really. if your in a building or something then claymore, but if your doing like headquarters you can put c4 where the headquarters are or whatever.
i think claymores are better if youre sniping because you dont have to constantly watch youre back, but theyre easier to run through where c4 if you know someone is in the area you can throw it and most of the time with c4 youll get a kill, i think c4 work well in headquarters because as soon as the enemy captures or is trying to destroy a headquarters wou can just lob a c4 up there.