Krav Maga kicks my butt once a week. It's hard, it's useful and it's a great way to release any pent up stuff you've been carrying all week. I usually limp around for a couple days after but it's worth it. It's mostly dudes and military/cops/bodyguards in class with me, so it's a pretty serious thing. I'm the only woman right now..
I'm currently a level 2.
I also work out in the gym 4 times a week but I take classes. On days when I'm tired or sore I do an aqua fit class, on days when I want to bring it I do boot camp stuff. I used to run, or do the weights and machines but I never got really good results until I started with the classes they offer at the gym. Now, I'm sore after each class and I thought I was beyond all that! So, in my opinion - that's what works.