Depending on the level of difficulty you are after, I enjoy Cardio and Weights when I am a bit low on energy and can't make up my mind what kind of workout to do. I love the music and the step segments, but it also includes compound exercises and upper body weights, as well as an ab/plank section at the end. If I am really (really) in the mood for a challenge, I think Hiit Circuit Lower Body from the RWH series is the hardest workout I own.
I'm looking for some to put into my running training.
My favourite leg circuit are Cardio leg blast, RwH lower body and Lower body blast.
To name few of them.