Unlockable Characters 
To unlock characters, do the following: 

Play as Patty:
Successfully complete Chapter 1 to unlock Patty. Her abilities are based on Nadia. 

Play as Rhombus:
Successfully complete Chapter 1 to unlock Cyrus. His abilities are based on Cyrus. 

Play as Vault Dweller:
Successfully complete Chapter 1 to unlock Cyrus. His abilities are based on Cyrus. 

Los: Slugger:
In the Shipyard Docks level in Los you can acquire a weapon called the Slugger 
which does 81-123 damage. Search the entire map to find a tiny alley (which there 
are many). This one is different, as there will be two fences as you go down. If 
you follow it all the way down you will find a footlocker containing a homemade 
laser rifle. Pick it up and return to where the fences are located. You will see that 
inside one of the fences is one of those ghouls with the poison on him. He is 
trapped and cannot get out. Kill him by shooting through the fence with the laser 
rifle. After he dies, you will get a message about an update on a secret. Then at 
the bottom of the screen where Boss names and health appear, it will 
read "Glowing Ghoul". Return up through the alley and a large ghoul will be there. 
He is easy to kill. After he dies, he drops the devastating Slugger weapon. 

Defeating the Raider Commander:
Use an incendiary cannon, two barrel shotgun, sledge hammer, and 35 stimpacks. 
Note: This was done with a level 9 Cain under the normal difficulty setting.

Easy experience:
In Chapter 4 in the garden, you have to escort a technician through a vault to 
open a escape hatch. Before you do this, make sure you have a Tesla Cleaver and 
the quest from the merchant to collect computer parts. Let the technician die 
anywhere in the level, then go to the last room (a room with three computer 
consoles and three robots that respawn ). Kill one of the robots and follow it back 
to see which laser barricade it came from. Stand about one character length from 
the lasers. The robot will respawn. Kill it as soon as it does. They are worth 50 
experience points and sometimes drop computer parts. Do this as long as desired. 
When you are done, just go back to the vault and trade in all of your computer 
parts for 100 experience and about 30 caps each.  

Carbon: Red Rider BB Gun:
In Chapter 1 when you are supposed to kill all the Raiders and save the 
townspeople of Carbon, rescue all them. Talk to the Vault Dweller after you get 
into the warehouse to get the Red Rider BB Gun with unlimited ammunition.

Unlockable Videos and Pin-Ups 
To unlock a level's cut-scenes, simply complete the chapter. Once you fully 
complete the game, you can access pin-up photos, and tons of concept art in the 
Bonus option of the main screen.