I'm a Brasenose student
And it is most definitely not dull. As people have said, as with anywhere you'll get people who love clubbing and going out, and people who don't. That's not just with colleges, that's with life. But almost any club night in Oxford, especially in the first term, tends to have a Brasenose contingent. A particular favourite at the moment is Camera, on Tuesdays and Fridays, but it varies from term to term and what's good at the time. Since everyone in the year pretty much knows each other (and an awful lot of people from other years), you're basically guaranteed to see another Brasenose face out. I imagine this is probably the same for a lot of college, but I can say it for us.
Quiz nights, we've done a few down the bar and they've been really fun, plus a few of us have been a couple of times to the pub quiz at Far From the Madding Crowd, which is a nearby pub, and Magdalen have an alternative quiz which is open to anyone from any college.
Also our bops are awesome, usually we have a few hours in the bar (last time with jelly shots and free uv paint), then went to Babylove which is a club literally just across the road, which was hired out and decorated just for us, plus some free shots there. So good!
So basically, BNC is awesome.