A few guys come to mind
1. Chuck Liddell - Defending his crown against Couture and sent him into retirement with a brutal 2nd Rd. KO , he also avenged his loss against Jeremy Horn at UFC 54 , defending his title 2x against 2 top fighters.
2, Georges St Pierre - He made Frank Trigg look like an amateur at UFc 52 , he was able to pull off a rather impressive victory over Sean Sherk and he was also able to beat a top P4P fighter in the world BJ Penn. He is finally getting his title shot that he rightfully deserves
3. Rich Franklin
4. Matt Hughes
5. Dan Henderson