In Fallout 3 where can you get energy weapons?

Answer 1

There are armories in just about every fort in the game (fort Independence, fort Constantine, etc.) each of these armories contain a entire weapon cash which generally includes some type of energy weapons.

Answer 2

There is a special plasma rifle that can be found in the REPCONN headquarters on the first floor but it requires you to either have 100 lockpick to reach or to go around on the second floor and drop down on the collapsed floor into the room. Also keep an eye out for recharger weapons they are energy weapons that instead of using standered ammo recharge over time which is useful if you are low on money or find it difficult to get ahold of energy weapon ammo. In just about the center of the southern edge of the map there should be a downed vertibird that is protected by about ten hardened robots, much more powerful version of the robots, these are the hardened mister gutsy models and the hardened protectron. Destroy them and by the vertibird there should be a much more powerful version of the arc cannon.