Pilates!! My friend and I decided to try this and we ran into two female friends of ours. Class had probably 20 people, 5 were guys. The instructor told us at the beginning that he has heard lot of guys whine after classes.
Anyways I found myself very stiff. Flexibility is definitely a problem, as was balance. The abs, back, and hip flexors got a great workout. Didn't mind it as I want to be more flexible, 'longer', and help better core strength/stability.
BTW, there were a number of very nice looking ladies, which didn't hurt ;-P. One gal came late and picked a spot in front of me. Very endowed, but her blue underwear kept sneaking out. Anyways, getting off topic.