1/2 liters... Triumph 675
3/4 liters... Gixxer 750
liter... I think this far in the game each brand has had a really great offering.
05 ZX10R
06 CBR1000 and the new ofcoarse.
06 R1
And the Gixxer 1k in all its incarnations was always a good choice...

Sport Nakeds...
SV650s - it has even its own race class
Z1000 - nothing gets you closer to a rough, unfinished, out of someones garage Street Fighter
Tuono - That much race tech should be allowed in a naked.