I recently started a sniping character and I am in New Vegas. And by now my old rifle just isn't doing it. Does anyone now where the Gauss Rifle is in this game? And could you give me directions as to where it is?

http://fallout.wikia.com/wiki/YCS/186_Gauss_rifle

It might of been abducted by aliens (you get the Unique Gauss Rifle or the alien blaster)

Heh

Personally I prefer the Alien Blaster to the unique gauss rifle because of how deadly the alien blaster is with the proper skills in energy weapons. Took out the 4 brotherhood guys that attack you doing the "I could make you care" mission for Veronica. Only took 1 shot from the weapon to kill the brotherhood guys and it has like 462dps and like 60 to 100 damage for me have to double check the figures.

if you have the wild wasteland trait, you will get the alien blaster if not you will get the uniqe gauss rifle

Do you have the Wild Waste Land pick? If so, you will not get the Unique Gauss Rifle. You get the Alien Blaster instead. I did read though that there is still a gause rifle avaliable if you take the WWL pick but not shure if it is true or not.

So i must kill the person using it, or steal it? Neither of which my EW character does.

Oh well, i just "buy" it from him instead
player.additem 15B38D 1
player.removeitem f 15000
:D

Problem is, if my character could additems from the console by himself, he wouldn't pay them...

He's hostile.