The Grim Reaper only appears in the missions "Numbers" and "Victor Charlie", but it is also used by NPC's in "Crash Site".
In Single player it is possible to fire up to 4 rockets at once, this is done by aiming down the sight and pressing in the LS/L3 and the number reel will change to 2, 3 then 4. Once you find the desired number of rockets to fire, hold the Shoot button down. This can easily be seen by aiming and shooting all 4 rockets in the sky.
In the multiplayer of Black Ops , the Grim Reaper can be obtained from a care package. It carries four shots with 8 extra in reserve and disappears after all shots have been fired or if the player is killed after using any of the ammunition. In the game mode 'Gun Game', the Grim Reaper is Weapon Tier 16. The Grim Reaper can be locked onto air targets. It is best used for air targets instead of random players; it's quite hard to aim at a moving enemy. Unsuspecting enemies will have a surprise but not enemies in wide open areas.
The Grim Reaper is semi-automatic and has extremely high damage. It's not advised to use this weapon unless a good spot to set up in is found. The Grim Reaper has incredible accuracy and holds 12 rockets in all.