Grab

The grab ability is the in game ability to move around objects. This can be used to make items easier to steal (moving them to somewhere where NPCs can't see, but you still lose Karma), move a corpse so you can eat it (if you have the Cannibal perk and don't mind losing Karma) or to move things around for aesthetic reasons (e.g. redecorating your house). An item can be grabbed by clicking in the right thumb stick on the 360 and PS3, or the Z key on the PC, while aiming at the item you want to pick up. Items may be grabbed whether or not you have your equipped weapon out. You are first instructed on grabbing items in the "Baby Steps" quest, and you can grab a lot of varied things in Fallout 3. You can grab corpses, barrels, and grabbing is a suggested way of nicely decorating your home in either Megaton or Tenpenny Tower. Milk crates occasionally contain valuable loot that is difficult or impossible to obtain without using grab. Another use for this is getting to otherwise unreachable ledges by stacking barrels, milk crates, etc. Heavier objects like Super Mutants are harder to move.

You can also use the grab ability to drop things at people from a height. They won't know you did it. A car tire from ten meters up can take down Jericho.