ANTS Profiler from RedGate Software is one my favorite tools since day one. Recently, I downloaded ReSharper 3.0 and it has found a place in my Toolbox already.
I like this part -
From the beginning, ReSharper has excelled in analyzing code on the fly. In addition to finding and highlighting errors, warnings, and warning-type situations in your code, now we've trained it to understand your code even deeper. ReSharper offers code suggestions - critical analysis of possible flaws in code design - with suggestions to improve them - all while you type.
Check out here for more details and free trial