Quagsire's my favourite, as you might tell from my profile pic. I have so many that I really like though.
Regice was my first shiny, and it's my favourite legendary by far. I love the whole concept of the regi trio, and think they deserve more love.
Whiscash is dope as hell too, just look at her smile. She's never let me down on an ingame team. She's the only Pokemon to have canon escaped the Master Ball too (in the great anime episode where she eats it)
The Whismur line as a whole is fantastic, I love Exploud though, his boomburst is incredible and look at all his amplifiers! Top level power there.
I really like the Cacnea line, Carnivine, and Maractus too, they're all great designs and really useful ingame. They're one of the mon that always find away onto my team as soon as I can catch them.
Ducklett's line is awesome. I love the transition from the cute but dumb af Ducklett into the graceful, powerful Swanna. Swanna pretty much carried me through the massive level spike in BW's post-game with Hurricane.
Durant is fantastic as well, I love its cry, its moveset is great and it has stats that make it very viable at any point of the game. Another Unova mainstay.
I'll stop myself there, but that's some of my top 20 at least..
