Any chance is it replica of the gun from "Gears of War" as that gun had chainsaw on.
A gun with a chainsaw attachment is still a gun, albeit with a bit more "oomph"...
paintballing ROCKS!!
What? It's a toy built by a sexless geek in his bedroom while his Mum sits downstairs in the living room worrying about the geek she has bought up and gently weeping onto the pages of her Take a Break magazine, sobbing for all the orgasms she never had.