When I first started yoga over a year ago, it was because I was stressed to the gills and having hip problems, and wanting to just make it all go away. Since then, I've gotten a lot better, and I've developed some favorite poses.
My favorite pose back when I started was Warrior II. I still have a fondness for the Warrior series, but lately, I've been preferring Plank Pose which, mho, is the quickest way to flat abs, and I also really like Downward Dog because I feel strong in that pose and am very proud of myself that I can hold it for long periods of time (our yoga instructor is very big on holding very a looooooooong time). However, I do have a new favorite: Sideways Plank pose.
I like Sideways Plank because not only does it tone, but it involves balance, and it's just really difficult to stay up -- it requires strength and concentration both. I'm getting a lot better at holding it, and I don't fall over any more -- or at least, it takes more than 30 seconds before my whole body starts shaking and I need to come down. This is another really good pose for abs.
I'm not terribly good at most of the balancing poses. I'm unable to hold Half Moon at all, for instance, but I'm slowly improving on Eagle Pose. Of course, it should be no surprise to anyone -- especially people who know me well -- that the pose I most look forward to is savasana or corpse pose.