If your there over the weekend, Sunday morning from 5am-10am the St. Pauli Fischmarkt has been going on since 1703 (I believe). It was a blast just to walk around and watch the fish auctioneers (more like comedians) selling combo's of fish wrapped in paper. People go from the bars to the market and continue to party. There was a great band playing the morning I was there. Hope you get to make it there. Picked up some funny gifts there too.
Have fun!