If you're into sports, /r/cfb and /r/nba are two excellent subreddits. /r/nfl is pretty good, but there's always some fights with the mods over what posts get removed, merged, etc. Nothing too bad, but there's a little more drama than the former two subreddits.

/r/motorcycles and /r/guns are good as well if you're into that sort of thing -- /r/guns is especially funny on the weekends ;)