Start the game with the "-console 1" command line parameter. Press [~] (tilde) while playing and type any of the following codes.
Note: Commands will auto-complete while you type them. Type any letter and you can scroll up and down with the cursor keys to see the various available console commands.

Code - Result:

impulse 101 - All Weapons & Ammo + Clothing
vchar_edit_histories 1 - Allows you to give your character a history during character creation, which provides bonuses and penalties to different stats.
vstats get animalism 5 - ANIMALISM discipline is Max Out
vstats get auspex 5 - AUSPEX discipline is Max Out
vstats get celerity 5 - CELERITY discipline is Max Out
vstats get charisma 5 - CHARISMA skill is Max Out
vstats get dementation 5 - DEMENTATION discipline is Max Out
vstats get dexterity 5 - DEXTERITY skill is Max Out
vstats get dominate 5 - DOMINATE discipline is Max Out
god or godmode - enable godmode
vstats get fortitude 5 - FORTITUDE discipline is Max Out
giftxp # - give # number of xp points
give item_a_xxxx - give armor of type xxxx
Blood 500 - Give Extra or Infinite Blood to withstand greater attacks
give item_w_xxxx - give weapon of type xxxx
give item_g_bloodpack - Gives character a BLOODPACK
give item_g_bluebloodpack - Gives character a BLUEBLOODPACK
give item_g_eldervitaepack - Gives character a ELDERVITAEPACK
noclip 0/1 - Go through walls.
vstats get intelligence 5 - INTELLIGENCE skill is Max Out
notarget 0/1 - Invisible to enemys.
cmdlist - List of cheats.
vstats get obfuscate 5 - OBFUSCATE discipline is Max Out
vstats get potence 5 - POTENCE discipline is Max Out
vstats get presence 5 - PRESENCE discipline is Max Out
vstats get protean 5 - PROTEAN discipline is Max Out
blood # - replace # with the number of points you wish your blood pool to be at. For example 'blood 4' sets your blood pool to 4 points.
vstats get thaumatury 5 - THAUMATURY discipline is Max Out
vstats get wits 5 - WITS skill is Max Out