I would say either a golden eagle or, come to think of it, a great ape.
I originally liked the eagle because eagles can go almost anywhere, are apex predators, and are protected by law almost everywhere - not to mention they can fly, which is so awesome. Remember, communication isn't the problem, as you can still use thought-speak. You would lose out on human things, but you would lose out on those types of things with nearly any animal. Still, I like the eagle because it can fly, it's protected, it has no predators, and it's not dependent on anything else - a wolf needs its pack, a lion needs its pride, etc.
However, the great ape argument got me thinking a bit. It's true though - an ape can still type, use human tools, drive a car, etc. They can't talk, but there's still thought-speak for that. However, it would be awkward and strange to be a part of society as an ape, as well as isolating - a human in an ape's body would be a novelty and always be in a crowd, put up on display. In all honesty, an ape-human would probably be famous - a celebrity, probably getting on TV and such. That's the only reason for an ape, though - if you can't tolerate being the one stared at like a handicapped child, it would be pretty bad. Living in the wild as an ape seems pretty bad - you sit down, eat some leaves and fruit and watch other apes do the same.
Living in the wild as an eagle seems better than that, and if you want to go somewhere that you couldn't fly to, such as a building (a theater, a museum, etc) you could probably just get a leather shoulder pad or a falconer's glove for a friend. Assuming they don't ship you off to some government lab, they will probably let the "talking" eagle inside.
So, it pretty much depends on what you're willing to sacrifice for what. Ape, at the expense of any privacy, or eagle (or any other animal), at the expense of being a part of human society. In either situation, you probably won't form any new relationships - hope you like your family and the friends you already have.
