The following are unlocked by completing the corresponding tasks during game play.

Unlock Amanda:
Complete Ghana's Time Trial

Unlock Amanda outfit:
Beat the Ghana Time trial

Unlock Amanda - Winter:
Complete Kazahkstan's Time Trial

Unlock Biker:
Complete the England level

Unlock Biker - No Jacket:
Collect 100% silver and 100% Gold Rewards in England

Unlock Biker - Red Jacket:
Collect 100% Silver Rewards in England

Unlock Bikini - Black (can only be worn in Croft Manor):
Complete the game, beat ALL Time Trials and collect 100% of Bronze, Silver and Gold Rewards

Unlock Bikini - White (can only be worn in Croft Manor):
Complete the game and beat ALL Time Trials

Unlock Cat Burglar:
Collect 100% Gold Rewards in Japan:

Unlock Classic Tomb Raider:
Collect 100% Gold Rewards in Peru

Unlock Classic Tomb Raider - Grey:
Collect 100% Gold Rewards in Ghana

Unlock Evening - Red:
Collect 100% Silver Rewards in Japan

Unlock Evening - Ripped:
Complete the Japan level

Unlock Goth:
Complete England's Time Trial

Unlock Goth Laced Shirt Outfit:
Beat the Japan Time Trial

Unlock Goth Outfit:
Beat the England Time Trial

Unlock Green Sport Outfit:
Beat the Bolivia Time Trial

Unlock Legend - Black:
Collect 100% Silver Rewards in Croft Manor

Unlock Legend - Blue:
Collect 100% Silver Rewards in Peru

Unlock Legend - Pink:
Collect 100% Silver Rewards in Ghana

Unlock Legend - Union Jack:
Collect 100% Silver Rewards in Bolivia

Unlock Pink No Coat Winter Outfit:
Beat the Peru Time Trial

Unlock Pink Winter Outfit:
Beat the Nepal Time Trial

Unlock Snowsuit:
Collect 100% Gold Rewards in Nepal

Unlock Special Forces:
Collect 100% Gold Rewards in Kazahkstan

Unlock Special Forces - Urban:
Collect 100% Gold Rewards in England

Unlock Sport:
Collect 100% Gold Rewards in Bolivia

Unlock Sport - Green:
Complete Bolivia's Time Trial

Unlock Suit:
Collect 100% Gold Rewards in Croft Manor

Unlock Suit - Cream:
Collect 100% Silver and 100% Gold Rewards in Croft Manor

Unlock Swimsuit outfit:
100% complete

Unlock Winter:
Complete the Kazahkstan level

Unlock Winter Amanda Outfit:
Beat the Kazakhstan time trial

Unlock Winter - No Coat:
Complete the Kazahkstan level

Unlock Winter - Orange:
Collect 100% Silver Rewards in Nepal

Unlock Winter - Orange (No Coat):
Collect 100% Silver Rewards in Kazahkstan

Unlock Winter - Pink:
Complete Nepal's Time Trial

Unlock Winter - Pink (No Coat):
Complete Peru's Time Trial

Unlock Bulletproof Lara:
Pull and hold LT and press A, RT, Y, RT, X, LB

Unlock Wield Soul Reaver:
Press and hold LB and press A, RT, B, RT, LT, X

Unlock Infinite Assault Rifle Ammo:
Press and hold LB and press A, B, A, LT, X, Y

Unlock Infinite Grenade Ammo:
Press and hold LB and press LT, Y, RT, B, LT, X

Unlock Infinite Shotgun Ammo:
Press and hold LB and press RT, B, X, LT, X, A

Unlock Infinite SMG Ammo:
Press and hold LB and press B, Y, LT, RT, A, B

Unlock One Shot Kill:
Pull and hold LT and press Y, A, Y, X, LB, B

Unlock Textureless Mode:
Pull and hold LT and press LB, A, B, A, Y, RT

Wield Excalibur
Press and hold LT and press Y, A, B, RT, Y, LT

Draw Enemy Health:
Pull and hold LT and press X, B, A, LB, RT, Y