i voted fawkes, cos i love the idea of the phoenix and he's just so noble and seems calming or something, part of the wisdom of dumbledore. yep fawkes will definitly become important. if he's lived forever (as phoenixes must, i assume?) think of all that he has seen and knows?
close second Buckbeak- well an extenstion of sirius i suppose (whom i mourn deeply as my fave character). also buckbeak just seems sweet.
i think any mythical creatures really appeal to me, love unicorns and well... thestrals are my new favourite additions. hence my name
actually any mythical creature that has a passing resemblance to a horse i am sure to love. oh yeah, why are their no horses in the harry potter universe?