Here is a list of Quake cheat codes

To use these open up the console (Hit the ~ key on your keyboard or use the menu, options, go to console to get to it) and then type the code in and hit the enter key.  Close the console (Hit the escape key).

• GOD = Toggles invincibilty on and off.
• FLY = You can fly.  Use the swim up & down keys to go up and down.
• NOCLIP = You can walk through anything.
• NOTARGET = Monsters will not attack you unless you attack them.
• GIVE S # = Gives you # number of shotgun shells.
• GIVE N # = Gives you # number of nails.
• GIVE R # = Gives you # number of rockets.
• GIVE C # = Gives you # number of cells.
• GIVE # = Gives you the # weapon.  (Example: 5 would give you the super nailgun)
• IMPULSE 9 = Gives you all weapons, full ammo, and keys.
• IMPULSE 11 = Gives you a rune.  You can only type this once each time you are in the console.
• IMPULSE 255 or IMPULSE -1 = Gives you Quad Damage.
• REGISTERED 1 = Makes game think you have registered version so you can open up barriers at start map and get lightning gun.  NOTE: Do not try to go into any slipgate episode higher than 1 unless you have the registered version!
• R_FULLBRIGHT 1 = All lighting in game is at max.
• MAP map name = Warps to map name level.  (Example: E1M1 would warp you to episode 1, map 1; END would warp you to the end of game; START would warp you to episode picker)

Try going to ID Software's web site for updates and patches on Quake.