I love Lanturn. Its stats are way too low to be a major threat to anybody, but Water/Electric typing plus Volt Absorb, on top of that wonderfully annoying Thunder Wave/Confuse Ray combo and (ridiculous synergy with Politoed), is just too much fun... plus it's just so damn cute.
I also like Leavanny, at least in the early game, for no particular reason at all. I like having a relatively strong and fast (at that point) pokemon who can use both Leaf Blade and X-Scissor... its come in shockingly handy, but I usually end up abandoning Leavanny for better pokemon at some point.
I love to run Absol and Umbreon, but just can't find movesets that work well for them. Absol has great attack and some sweet slash moves, but is too slow and frail to really use them, and Umbreon... I think game freak just hates Umbreon. It started out pretty sweet, solid defensive stats, the best movepool and Special Attack stat among Dark types (which was greatly significant in G2), access to Snatch, Taunt, Crunch, Mean Look and Perish Song... but now I look at what Umbreon has been through and it makes me sad (I mean come on GameFreak, hidden ability INNER FOCUS? you give Espeon Magic Bounce and you can't even give poor old Umbreon something useful? not even Prankster? And don't even get me started on the logic behind giving it Synchronoise... It's almost as sad as Flareon).