Why do you think that traditional martial arts don't work in actual combat?
Don't do Martial Arts for actual combat, you'll be dissapointed. But do it for fun, or conditioning or something else maybe competition.
Also you should look at your personnality and physical ability to pick which to start of with. Like Judo, for example you'll probably do nothing but practice taking fall.
TaiChi you'll be given sets and stuff, it can get boring, but if internal stuff interest you, really nothings beat TaiChi, oh make sure you get a certefied instructor in Chen style, at least Chen style was actually used for the self defense of Chen village from bandits, and that village survive till today, so the style probably work.
If you like contact, go take boxing or Thai kick boxing, it'll probably more fun for you.