Muscle Milk Vanilla and Strawberry, and the Evopro isn't bad either, the vanilla at least. I like a vanilla base because you can add fruit or yogurt to it and beef up the calories some, but they still taste good.
If you are going to buy Optimum Nutrition, which I suggest you do, get their Pro Complex... More protein and it tastes a bit better. But all of their products taste good, so you'll be happy either way..
I'm really loving Syntrax Nectar. I've only tried Caribbean Cooler, but there are immediate plans for the very near future to try different flavors. It's like having a virgin mixed drink, which is way cool in my eyes.
I like myoplex's stuff and ABB drinks are awesome but very spendy http://www.americanbodybuilding.com/p.asp As far as powders go I dont really care about taste as long as it mixes smooth with no chunks...I hate chunks