In the Fallout series of RPG computer games, there are many references to Monty Python. One of those is a special random encounter. You meet some men in power armor: they are knights, looking for the "Sacred holy hand grenade of Antioch". What most people don't know is that the weapon actually exists in the Fallout 2 game code. It's not available during the adventure, though: to get it you have to cheat, using the "Fallout 2 inventory editor" program.
It is thrown like a normal grenade, but deals an ungodly amount of damage (500, if memory serves me right), and will destroy most critters in one hit.

15/08/2005:
After a long time, I have reinstalled Fallout 2 and am in the process of replaying it. Since the last time I did so, the gamer community has managed to find the special random encounter in which you can get the grenade. It was meant to be available in the game, but in the end wasn't, although it isn't sure whether this happened because of a bug/glitch or on purpose. Anyway, a mod has been made to activate said special encounter. Look for it in Fallout sites.

The holy hand grenade is also featured in the game "Wizardry IV", although it is portrayed as the "holy hand grenade of Aunty Ock".