The gutters on your home are constructed of several pieces of corrugated steel. They are riveted together. A rivet is a metal pin with a small head on it. A rivet gun secures the metal rivet into a pre-drilled hole. There are very few ways to remove a rivet once installed. However, it is possible to do so with a hand drill without causing damage to the gutter.
Secure a drill bit to your hand drill that measures slightly larger than the hole in the center of the rivet.
Center the tip of the drill bit over the hole on the center of the rivet.
Drill straight through the rivet. The drill bit will remove the center wall of the rivet.
Pull the remaining piece of the rivet out of the hole with a pair of needle noise pliers.