Here are a couple of Scaled composite's aircraft that would be really cool to fly. some of them may be a little hard to model i know, but I know someone could do it if one hasn't been done.

http://www.scaled.com/projects/proteus.html
http://www.scaled.com/projects/vjetii.html
http://www.scaled.com/projects/vantage.html


Also,
Has anyone seen a good free model of the RQ-4 Global Hawk? I can only find Kaz ito's Barely converted FS2k2 model.