My favourite is a :keano: smilie from a Man Utd forum, which I can't link to because it's restricted to logged on members. I'll see if I can lay my hands on a copy.
:down: :irritate: and are the most expressive of the ones here. I tend to use a lot though.
and 
and 
and 
are the best-but I think this is the first time I've used 
is my fav....
and 
