Heh... I wouldn't mind a plasma shotgun...
And a spiked baseball bat. That wold work well with the workbench: 1 baseball bat (20) railway spikes.
Also a time bomb off of l4d where everyone just crowds around it and BOOM!!
Its still beta, but it works (in FO3).

http://www.youtube.com/watch?v=Al3qhaMHn6A
http://www.youtube.com/watch?v=eTzfyevGNtI
http://www.fallout3nexus.com/downloads/images/7751-1-1248217696.jpg
http://www.fallout3nexus.com/downloads/file.php?id=7751
(I never got around to making it craft compatible; but I'm going over my old projects to try to get them all polished up.)
For New Vegas I have three weapons that I plan to make... One is http://i271.photobucket.com/albums/jj125/Gizmojunk/500px-MatrixAutoShotguns-3.jpg