Lightsaber

Lightsabers are tools specific to SLASH'EM, whose skill is restricted for all classes.

Use as a weapon
The four varieties in increasing order of damage are: green, blue, red and double red. They are a high-damage weapon, but have a -3 to-hit penalty (-4 for double reds). They turn off automatically when they are unwielded, although if you are fast enough, you can dual-wield them, or even stick one in you bag of holding! (Note that this currently does not damage your containers in any way...)

Use as a tool
Lightsabers can be used to burn Elbereth infinitely, making them invaluable, even when not used for combat. They can also be used to dig!