how about a Savage 124 straight pull boltaction 12ga shotgun they only made them in 12ga.
Or a fast shooting Kessler Model 50 Levermatic came in 12/16 and 20 gages!
it may not be new but would shure be the talk of the range!
I bought my 870 express for about $320 new at a local gunshop,that's about what they are going for unless you go to a huge superchain that offers sales.