I play headquarters a lot so I generally use claymores.

I use 3 specials, bomb squad, bandolier and 3 frags depending if that perk is unlocked or not.

3 specials, with stuns of course.

bandolier as I use the AK 47u and that goes through ammo quickly.

the leader would be x3 frag....i hate cod

Just x3 frags.

I always use claymores.

C4 for me, this is on the PC version FYI.

I mainly play on the map Pipeline as I tend to own in TDM on it, claymores are critical when going around in the tunnels, otherwise you will get shot in the back, I probably get 1 kill for every 4 claymores I drop (at least).

C4 is great in Domination. I throw them down near my team's flags. When somebody starts to take it, BOOM! It lets me be in two places at once. It can be even more effective if you wait a couple of seconds after the flag starts to blink, because other enemies might arrive too, giving you a chance to get a double kill.

Other game modes, 3X frag or claymores.

I always play hardcore so I try not to use grenades too much. Claymores are much safer..lol

RPG just becuase really

Bomb squad because it is clearly the most efficient. 

RPG's.
 
I like to see people become sad when their Helicopters fall down to the ground in a matter of seconds.

Lately I've been using the frags on the rare occasion I play.

I'm using claymores to prevent ambush from behind, or sometimes lure people in front of me that I'm running away, while there's a claymore waiting for them behind the next corner.

Bandolier for me, seeing all i do in that game is spray bullets everywhere that perk is essential for me.

3 stuns for my assault/stealth classes, claymores for a sniper, and RPG's for my shotgun class or whenever I feel like blowing people up.

Bandolier on EVERYTHING. I live way too long not to when I play for keeps, meaning I spray like a motherfucker and try to pick people off at ranges way too long for my gun >.>

for the most part its claymore because i play hardcore search and destroy the most and i have highly strategic places on all the maps to play them and many you may have never though of. But if i want to play headquarters or domination etc i use special grenades X 3 (stuns) so i can constantly slow the enemies down. i capture points like crazy, get ton of kills, and more assists than anyone. 
 
ps. bandolier?? sounds like a lot of n00bs in here! i bet you're all packin n00b-tubes as well. 

Bandolier most of the time or Bomb Squad if I'm playing a more run and gun/stealth class.

bandolier is the only useful one

Bomb Squad.  Got sick of getting killed by something that wasn't someone shooting at me.

Bandolier, I always use M-16 w/ red dot, usp .45 , bandolier, stopping power and martyrdom

I use bomb squad for the most part, but occasionally I will use RPGs because people get really frustrated when you kill them with it. Also, they are generally pretty useful to take down helicopters

 
I use Bandolier.
 
You know.....
 
Bigger mag is kinda you know...awesome.

claymore

 Bandolier,  silenced P90, steady aim and UAV jammer. Gets the job done nicely

" Just x3 frags. "

Claymore for sure.

Bandolier motherfucker