Honestly, most of the emotes on here are pretty ugly. Which is why I normally tweak the smilies I make so that they don't parse into those things. There's a few exceptions, though.
My Favorite Emotes

because cuccos. Oh, and Locke used to use them on mod-edits on my shouts way back when, so I'll occasionally use it for that.
<3 because heart containers
:cooky: because those eyes
:bleh: because better tounge emote than

because Arsenic
:? because Chlorine

because portable network graphic

because

nion: because blarhg my fourms kep getting delted

because licking emoticon by yours truly ♥
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My Least Favorite Emotes

because face looks smashed

for the same reason

because Tantalum

because Tantalum

because Ununhexium always uses it when he's making innuendos, so I feel like a pervert using it
:puppy: because hideous

because it looks like a GFCI outlet
:huh: because badmuffins used it along with flaming me

because octagonal
:love: because buck teeth

because badmuffins
:ganondorf: because you can't represent his amazingness with a 19x19 pixel GIF and it looks nothing like the guy