Stare+Tag

This can work with a group as small as 5-6 people, but is good for a group as large as 20.

Have the group stand in a circle shoulder to shoulder. Decide on a code word as a group like banana. Tell the group to stare at the ground. When you say the code word, everyone in the circle will stare at one other person in the circle. If two people are looking at each other they are both out. The round continues until there are only 1 or 2 people remaining.