The cryo grenade deals only one point of damage to targets, but will freeze them solid for three seconds. It can be used to get a few easy shots on foes, or to freeze a non-player character in order to pickpocket them. Reverse pickpocketing a cryo grenade or a cryo mine into a character's inventory will also freeze them.
Cryo grenades share a number of characteristics with all grenades:
They may bounce or roll unexpectedly if not thrown carefully.
They can be thrown through doorways or bounced around corners to attack enemies who cannot see you.
They can be targeted in V.A.T.S. and thus shot out of the air.
Shooting them while they are still held by the enemy can detonate them as well.
Grenades can be thrown point-blank in V.A.T.S due to the sharply reduced damage taken.
A grenade that has been thrown toward you will show up on your HUD as a red arrow denoting its direction relative to you. Move in the opposite direction as quickly as possible to escape the blast radius.
Holding the fire button down for a longer period of time will increase the strength of the throw.
Grenades can be thrown for longer distances than normal through successful V.A.T.S. hits.
Grenades in Fallout 3 cannot be "cooked," that is, timing the detonation by holding onto the grenade after pulling the pin.
It is possible to plant a live grenade on a non-player character by passing one from your inventory to the non-player character's inventory via reverse pickpocketing.
These grenades can be obtained from Elliott Tercorien after releasing him from stasis and going through the cryo lab with him. He will pick up some cryogenic parts in the area where Beckett and Daniels are frozen which enables him to start making the grenades upon return to the engineering core. He will give you 3 cryo grenades and 3 cryo mines after you wait an hour for him to make them. After that must wait another 3 hours for him to make 2 more each time you ask. Elliot will not be able to make any more cryo grenades or cryo mines after he leaves the engineering core during the quest This Galaxy Ain't Big Enough....
The cryo grenade was originally a weapon cut from the final version of Fallout 3. It does not exist in the final version of the game, nor does it exist as an unused item in the G.E.C.K. editor. The mesh and texture are contained within Fallout 3's BSA files, but these files were not used, as new meshes and textures were made to replace them in Mothership Zeta. Another cryo weapon, the cryolator, exists only as a mesh and textures in Fallout 3's BSA files.