At my office, we play darts and drink beer for the last hour and a half of every Friday. The majority of the time everyone is there and we spend a lot of time chatting while we play. It's fun and I really think it keeps everyone friendly, it's that much easier to remember the other person is a real person when you disagree.

Sometime people go out to a bar or something afterwards. I may feel like I'm missing out but it never feels like something I "should" be doing.