Specifically from high schools or colleges, students are handed a packet and given a few weeks to choose a ring, stone, and designs that represent themselves the most. Usually very expensive, unless you're a rich bastard...
Student 1: Hey did you get a class ring?
Student 2: Yea, I got a 10 carat diamond stud on it too!
Professor: You rich bastard!
To wrap one's penis around a finger so it resembles a ring on a finger. Commonly used in the penis showing game.
Kirk tricked Bob into looking directly into his Class Ring. Resulting in Kirk being able to kick Bob's ass twice for being gay.