I like forms. I spend much of my time practicing by myself, so forms play a big role in my practice.
Favorite is a tough one to name. All in all, I guess I'd have to say it would be Chut Yap Bo Kuen, The In and Out (or Back and Forth) Fist, from Tibetan White Crane (my spelling might be a bit off, but ya get the picture).
What do I like about it? It is very fluid and contains much of the real "meat" of the system. My sifu says that his uncle would say that it all comes back to this form. The whole system is in there. I love the long-arm fluidity of the set, which is really characteristic of the system. It is done very fast, like you are running sprints, and it is very long: the fastest I have ever done it timed, was 1 minute, 45 seconds, done at full speed, and is exhausting, like sprinting a half mile. Sifu always says that I need to be faster. I kind of like the fact that it is tough for most people to even get thru it, due to the length.
It took several months to learn each half of the set, and I am still working to perfect it after about 6-7 years.
I have also recently learned Fu-Hok (Tiger-Crane) from Hung Gar, and I like that one a lot as well. It also took several months to learn from start to finish. This one needs A LOT more work, since it is so new to me, but I really like the tiger techniques. I'd probably have to put this one in second place, for favorites.
I know that Tibetan White Crane has some drunken material, and I would love to learn that while I am still young enough to be able to do it. Not sure if that will ever happen, tho.