Everyone has their favorite drill at the NFL combine, but the ones that usually are talked about the most are actually some of the least effective in evaluating many positions. The 40 yard dash, for example, is mostly just a bragging rights competition between primarily defensive backs and wide receivers. Rarely does anyone get to really just open up and sprint on the field, and who knows if they are as fast as they looked in underwear when they have all that heavy gear on.
For most positions, the drills that test short range agility are the ones that really come into play in a game situation.