Lethal equipment in modern warfare 3 comes with many options including a Throwing Knife or a Bouncing Betty.

Frag
Cookable frag grenade.
Unlocked: Default

Semtex
Timed sticky explosives.
Unlocked: Default

Throwing Knife
Throw it and pick it back up.
Unlocked: Level 5

Bouncing Betty
Launches into the air before detonating.
Unlocked: Level 37

Claymore
Proximity activated explosive mine.
Unlocked: Level 53

C4
Remote detonation explosive.
Unlocked: Level 69