If you’re riding and racing regularly and tend to get covered in mud, then a good pair of grips will help you keep control of your bike even if you have slippery crud over your hands. 

Aggressive grips have lots of surface texture, and the lumps and bumps will help you hold on. However, some people find them uncomfortable to ride with, especially over long durations. A good compromise are the Race Face Good N Evil grips; lumpy for grip on one side, smooth for comfort on the other, and they’ve got a damn cool name.

The ESI Grip is a good option if you want something that will stay grippy when wet, but without the bumps and knobbles of other more aggressive handlebar grips.