Half Life 2 save - this save will unlock all chapters and the video to Episode Two.
Half Life 2 trainer - press the key on the NUMPAD to get the following:
0 - 100 Health
1 - Infinite Armor
2 - Infinite Health Aide
3 - Infinite Ammunition
4 - Infinite Auxilary Power
5 - 1 Hit Kills
6 - Enemy Freeze
7 - Low Gravity/Super Jump