"Best" 20-minute workout

I've just started my sixth month of Insanity. I absolutely LOVE this workout!!! I did month 1, then month 2, the first round, just as recommended. The second time, I did month 1 twice, and then month 2. Now I'm back to month 1. I've lost twenty pounds, and am just getting such good results. I currently work out first thing in the morning, before I go to work, which works best for me. Right now, I am making fitness my #1 priority, but I would also like the ability to be a bit more flexible in the future. After my mom had her four children, she got back into amazing shape by doing the "20-minute workout" that was televised each morning. She said it was a very intense, but short workout, which worked with her schedule as a stay-at-home mom of four children. What is THE best, the hardest, and most intense 20 minute workout you know of? If it doesn't require a lot of extra equipment, all the better, as I'm not too crazy about purchasing a lot of new stuff. Another reason why I LOVE Insanity. I'm looking for something that just cuts to the chase, and is intense for the full 20 minutes, giving me a great workout, but not taking up quite so much time. Any thoughts or ideas?