The Maliwan Volcano! It the manufacturers legenadary Rifle. Comes in many flavours of body type, model and differing prefixes.
Also Look out for these, You'll want one of each (and will find better versions of) ;
The Pestulant Defiler (thats a mispell I think) A Revolver.
The Hellfire, An SMG
A Saviour , Another SMG. possibly with elemental type.
Once you're 50 you'll trade the Volcano for a 'Wrath'. Unlike the Former, the Latter comes in 4 different elemental flavours. Try the Liquid Wrath!
Dont know what I'm talkin' 'bout. You will in time. (or look in here