Astrobase Go! has a free boxy and un-realistic Astro Ray Gun papercraft on their site :) I don't really know whats going on with that sight (besides the t-shirts and cds), I think they're an offshoot for the Venture Bros. animated tv series.
Hat tip to reader Bill for sending it in. Follow the link below and look at the bottom right corner of the pic.
Retro Ray Gun Papercraft
Hellboy Papercraft - Samaritan Gun [Related Posts]
Perfect Dark Papercraft - CMP 150
Starcraft 2 Papercraft - Terran Marine Cannon
USMC M40 Sniper Rifle Papercraft
Perfect Dark Papercraft - MagSec 4