From The TimeSplitters Wiki

Sci-fi Handgun
Ammo	30 Energy Cells/200 Energy Cells
Fire Rate bullets per sec/cartridge time	N/A
Reload Time	N/A
Damage (per Single Shot) Head/Body/Leg	N/A
Type	Pistol
Zoom	No
Primary Fire	Fires energy cells
Secondary Fire	Fires engery cells
Games	TS2, TSFP

Generally recived as a bad weapon ill-suited to the fast-paced action in TimeSplitters 2, the Sci-Fi Handgun is more of an experiment then a proper weapon. It fires a burst of 3 slow-moving, weak shots with each pull of the trigger. The shots ricochet off of walls and floors, bouncing around a few times until dispersing or hitting a target, regardless of whether or not it is the player who fired them. In a slower and more tactical game, they could be a great addition for firing around corners without exposing oneself and risking injury, but in TimeSplitters 2 they are usually more of an annoyance than an actual help.

The TimeSplitters: Future Perfect version of this weapon is a vast improvement over the TimeSplitters 2 model.

Also, In TS2, with an Action Replay, a beta Sci-Fi Handgun can be found. It's primary fire was an orange blast, and secondary shot 3 green orbs in a linear area, and all 3 hitting an enemy killed them in one shot.