Arm bomb

From Wormhole Sci-Fi MUD Homepage

This must be done before a bomb is wielded and thrown using the grenade throwing skill. (Alternatively, you can just drop the bomb, and leave the room.)

Without this skill, you won't be able to initiate the countdown on any explosive device. Also, people with a low level of proficiency run the risk of detonating the bomb instantly... which is messy and always amusing.