Thief (Fallout 3)

Thief is a Fallout 2, Fallout Tactics, Fallout 3 and Lionheart Perk.

Fallout 2 and Fallout Tactics
The blood of a thief runs through your veins. With the Thief Perk, you get a one-time bonus of +10% (+10 skill points in unpatched Fallout 2) to your Sneak, Lockpick, Steal, and Traps skills. A well rounded thief is a live thief.

Fallout 3
With each rank of Thief perk, you gain an immediate bonus of 5 points to both the Sneak and Lockpick skills.

Lionheart
The blood of a thief runs through your veins. With the Thief Perk, you get a one-time bonus of +10% to your Lockpick, Find Traps/Secret Doors and Sneak skills.