From The TimeSplitters Wiki

Brick
Ammo	20
Fire Rate bullets per sec/cartridge time	1
Reload Time	N/A
Damage (per Single Shot) Head/Body/Leg	5%
Type	Other
Zoom	No
Primary Fire	Throws Brick
Secondary Fire	Throws Brick Further
Games	All

The Brick has appeared in every TimeSplitters game so far as an unlockable weapon in the Challenge: Super Smashing Great: Don't lose your bottle and used in Challenge: Avec le Brique(same challenge category with Don't Lose Your Bottle). It has a short range, and weak attack power. The secondary fire shoots at a higher angle. When aimed at a wall it will ricochet and hit the player, causing ironically large self-damage.

Weapon Tips

The brick is some what funny. You can throw the brick at different distances. If aimed at the head, it could kill instantly. It's good for a group of people, so the brick can bounce off each person.