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

To unlock various pistol upgrades collect the corresponding amount of rewards.

Increased Magazine Capacity:
25% of Silver and Bronze rewards

Increased Accuracy:
50% of Silver and Bronze rewards

Increased Damage:
75% of Silver and Bronze rewards

During game play enter the following codes to get the corresponding effect.

Bulletproof:
Hold L, then press X, R, Triangle, R, Square, R

Unlock One Shot Kill:
Hold L, then press Triangle, X, Triangle, Square, R, O

Draw Enemy Health:
Hold L, then press Square, Circle, X, R, R, Triangle

Unlock Infinite Assualt Rifle Ammo:
Hold L, then press X, O, X, R, Square, Triangle

Infinite Shotgun Ammo:
Hold L, then press R, O, Square, R, Square, X

Unlock Infinite Grenade Launcher:
Hold L, then press R, Triangle, R, O, R, Square

Unlock Infinite SMG Ammo:
Hold L, then press O, Triangle, R, R, X, O

Unlock Excalibur:
Hold L, then press Triangle, X, O, R, Triangle, R

Unlock Textureless Mode:
Press and hold L, then press R, X, O, X, Triangle, R


Tomb Trials Unlockables
Complete the following tasks in Tomb Trials mode to unlock the corresponding items.

Unlock Biker, Brown Jacket Outfit:
On Medium setting difficulty complete Bolivia in Treasure Hunt mode

Unlock Silver Gallery:
On Easy setting difficulty complete Bolivia, Croft Manor and Fiery Maze in Treasure Hunt mode

To unlock the cheats in the 'Specials' menu complete the corresponding tasks.

Unlock Textureless Cheat:
Clear the game on any difficulty.

Unlock One Hit Deaths:
Clear Bolivia (stage 8) under 4:15 in Time Trials.

Unlock Infinite RC650 Ammo:
Clear Japan under 12:15 in Time Trials.

Unlock Show Enemy Health:
Clear Bolivia under 12:30 in Time Trials.

Unlock Excalibur:
Clear Nepal under 13:40 in Time Trials.

Unlock Infinite Shotgun Ammo:
Clear Ghana under 20:00 in Time Trials.

Unlock Infinite MG415 Ammo:
Clear Peru under 21:30 in Time Trials.

Unlock Infinite Grenade Launcher:
Clear Kazakhstan under 27:10 in Time Trials.

Unlock Bulletproof Lara:
Clear England under 27:00 in Time Trials.

Unlock the Soul Reaver:
Clear the game and complete ALL Time trials.

Unlock Amanda:
Finish the Time Trial in West Africa.

Unlock Amanda (Winter):
You must complete the game getting ALL secrets and defeat ALL Time Trials.