Use a small knife such as a paring knife to cut around the stem in a circle. You'll want to cut deep enough to get the ribs, but don't cut into the center. Cut straight down into the pepper.
Use your thumb to separate the top of the pepper from the body.
Grasp the body and top of the pepper firmly in different hands and pull the top off, separating the ribs and seeds from the body.
Simply pull out any remaining ribs and you are good to go!
Ta-da! Faster Fajitas!