Cheats for Tomb Raider I & Tomb Raider Unfinished Business (PC & MAC)

Cheats
2 Cheats

Walk one step forward, one step back, release walk and turn around three times in either direction (left or right arrow), then jump forward (Alt + up arrow). Walk one step forward, one back, release walk and turn around three times in either direction (left or right arrow), then back flip (Alt + down arrow). (NOTE: This cheat does not give medipaks. You can use a savegame editor to add extra medipaks.)
 * Level Skip
 * All Weapons and Ammo

Note To Macintosh Users: If you're using the numeric keypad controls and are having trouble with these cheats, try doing them with the regular arrow keys.

PC and Mac Savegame Files: An alternative to cheat codes is to download a save file from just beyond the spot where you're stuck.

PC Savegame and Position Editors: Edit your save files to add weapons, items, health, change Lara's status (air, on fire), or reposition her anywhere in a level. Savegame Editors

Source
http://tombraiders.net/stella/cheats/TR1cheats.html