Display It
There's probably not many people who would display a glass eye as a decoration. It's something you would see in a movie or TV show like "The Addams Family." One idea is to draw a face on a piece of wood. Glue the eye to the wood where one of the eyes would go. Glue a fake nose, mouth and eyebrows on the wood. Draw a line in place of the other eye. It would make for a funny, odd, interesting piece of art.
Third Eye
All you need is a little hot glue and you can make a third eye. Get a headband of your choice and hot glue the glass eye to it. Another option is to get a ski cap, glue the glass eye to the front of the cap and pull it down low on your forehead. If you want it to look like it's glued to your forehead, get a matching flesh-tone skullcap and glue the glass eye to it.
Party
It would certainly come as a surprise if you coughed up a glass eye at dinner. The ideal setting for this kind of prank would be a party or holiday get together. Keep the glass eye in your pocket until dinner is served. Use your napkin to cover your mouth while you slip the glass eye in. Start to fake a cough to the point where people stop talking or get up and start to pat you on the back. In one heave, cough the eye into your hand. Watching your friends and family's shock will make for an entertaining party.
Video Pranks
Film a video of you playing pranks on people with the glass eye. Put the eye in someone's food and film their reaction, or give it to a person as their birthday present, complete with fancy wrapping. When they open it, the surprised look on their face will be worth filming. Film yourself wearing it and asking someone for directions. Of course, you can always glue it to your dashboard.