One of my brothers found this amazing creation:
http://www.fashionerfilms.com/05design/cro...rossbow_frm.htmI think a DS Lego version could be made to fling flaming plastic bricks (just kidding). Seriously, it would be a fascinating project to design one.
I love Legos, and am digging through the garage trying to find the boxes filled with them, once heavily used back before my kids became teenagers.
Besides a Lego DS gun, it would be fun to try and construct Dome City with them. A good friend, now an architect of some stature, built the Hades opening landscape, with Tyrell Building, from Blade Runner out of Legos. I still have a Lego Police Spinner, with opening doors and complete with cop and a fake box he gave me, so these simple toys really do have a lot of potential. ;)