Langenschwert
Master Black Belt
It of course depends on what's near you. As a general rule, Boxing and Judo clubs are of generally high quality, and will give you a good foundation for basically anything. Straight up wrestling is a great (or perhaps the best) option, can't go wrong with that. Just remember that being great in a sporting art doesn't make you a self-defence expert, though it will prepare you very well to learn it quickly. Don't forget weapon arts, too... it's a pretty good reality check since some arts' weapon defence is shall we say... optimistic. Once you've learned how to use a knife or a sword or a stick you'll start to see how AMAZINGLY good you'd have to be at weapon defence to make it work against a skilled, armed attacker. For weapon arts, make sure they don't just take an unarmed form and stick a weapon on it. That's a huge red flag run up a flashing neon flag pole. Most importantly, find something that's fun and you enjoy training in... that way you'll actually show up to train.
-Mark
-Mark