Keys are for Cowards

Keys are for Cowards is an achievement/trophy in Fallout 3 which is awarded for successfully picking 50 locks.

Hints

 * 75+ Lockpick skill is an advantage.

Places with many doors to lockpick

 * Megaton - Try going here at night. Various houses are easy locked and can be lockpicked easily. Also check inside, as there are some locked objects in the houses as well. Ex: Cash Register, Refrigerator, etc. You will lose karma doing this.
 * Minefield -There are a few doors you can pick here. As well as a safe under the bed of one of the houses. Also, one of the 3 buildings contains a dollhouse that you need a lock pick skill of 100 to open.
 * Rivet City - At night. The door to Rivet City Market, and a decent total of doors on the Upper Deck (most of them are easy locked as well) like Sister's Hotel Door, Hotel Room Door, Zimmer's Hotel Door, Doctor Preston's Door, Flak & Shrapnel's Door, Doctor Li's Door.
 * The Midship Deck has a few: Seagrave Holmes' Door, Door to Rivet City Market.
 * Tenpenny Tower - Cash register.
 * Underworld - Cash register, Safe. (Both hard locked, and both located in Carol's Place)
 * Little Lamplight - Two easy locked ammo crates in the middle of the Great Chamber.
 * Capital Wasteland - Exploring and scavenging every single building you come across can be very helpful, many buildings contain at least three locked containers and one locked door.
 * Super-Duper Mart - The mart contains lots of locked ammo containers scattered all around.
 * Vault 87, Vault 92, Vault 106 and Vault 108 - These vaults contain lots of locked doors, decent amount of locked metal boxes/first aid boxes/ammo boxes.
 * National Archives - Various safes in the lower levels containing documents.

Exploit
There is an entry to the Broken Bow of Rivet City south west of Rivet City across a bridge. The door is locked "Very Hard" (requiring a Lockpick skill 100) on both sides. From inside, there is a power switch to the right of the door which unlocks and relocks the door. If re-locked via the trigger, the door will drop to "Easy" for unknown reasons. You can re-lock the door and pick or force pick (85%) it an unlimited number of times for an easy achievement.