Roserade is my favourite because...well...just look at this:
[img139]http://img.photobucket.com/albums/v221/Gravyyy/rosey.png[/img139]
C'mon, that's just the definition of cool, right there.
Yukimenoko comes in a close second, due to the fact that it's somewhat more usable than Glalie, has an interesting type combination, looks the bee's knees and is based on an interesting legend.
I'm also fond of:
Eteboss - Phallic Phinger Phun!
Weavile - If 'I think it looks swell!' counts as a decent enough reason, I'm using it.
Donkarasu - The fact that they actually went so far as to create a pimp pokémon makes it an instant winner.
Muumage - Anything that can swallow a Rugby ball and keep it their throat without bursting into a fit of panic, will gain my respect anyday of the week.
Manmuu - Makes the Piloswine evo line somewhat interesting.
Elblade - Swordfighters, chivelry and a taste for ballet. A formula that one should not mess with.
Glion - I like that funky 'gargoyle' look it has going on. Though in the long run, I prefer Gligar.
Elekman - He's got the master plan, AND he hates that Sheimi!
Dainose - For being there.
Megayanma - YANMAMON DIGIVOLVE TOOOOO.....MEGAYANMAMON!
Jibacoil gets honerable mention for being everything that Magneton should have been.
Come to think of it, I think the only evolutions I really don't like at all are Dosydon, Mojanbo and PorygonZ. And that's only down to the fact that I never liked their pre-evolved forms anyway, and that I've always despised the idea of a virtual pokémon.
And before anyone jumps to conclusions....no. I wasn't suggesting that Megayanma looks like a Digimon.