From The TimeSplitters Wiki

The Glass Smash Challenges all focus around breaking windows, with S47 grenades and with Bricks in the fastest times possible. There are slight differences in the distance a grenade goes in the NTSC and PAL versions of TimeSplitters 2, allowing NTSC players to achieve slightly better times.

The challenges in Glass Smash are:

• Pane in the Neck
• Bricking It
• Stain Removal