My favorite so far has been a pair of VZ "Operator II" grips. Pure functionality - not necessarily pretty to look at, unless you find functionality to be beautiful.
"Aggressive" means that the grips dig into your skin. There are little spikes where your fingers go... It may cause your fingers/hands to burn a little, but it's easier to hold onto the gun during recoil or sweaty conditions. I believe comfort isn't necessarily important when choosing your grips.
They are a little on the pricey side...