Here's what comes to mind, assuming you're already using EVE which overhauls all energy weapons in the game, that one's a must-have. Anyhow:
I really like the scope on this one http://www.nexusmods.com/newvegas/mods/36020/?
Check the author's page too, he's made more weapons like that as well.
Wonder Weapons from COD Zombies:
https://www.youtube.com/watch?v=bgZADZVPsq4 (link in description)
Ray Gun Mk2, same thing as above:
Mad Science, this mod has plenty of interesting looking Energy Weapons:
If you like Star Wars stuff:
MNK-RHINO Gauss Revolver:
_________________A secret message to the chosen ones: