Good sentiment USP. There are a lot of good lists here already (and covering just about every category of firearm).
Nice list freakshow...didn't know they made the mp5 in 10mm (just googled it and found a .40S&W too).
You're right Scout, they will be able to improve it. I don't ever see them being sold to the public though. It would be cool, but I think there are too many nefarious uses, and too few practical ones. I could be wrong though.
And one more addition to my list (blatantly stolen from DakotaRanger's list)
a Browninig M2 (or possibly one of the new and improved FN M2's)