I love Buizel & Floatzel - they are my favorites from Sinnoh - mostly since I love water types and I also love weasels & otters, its what both Buizel & Floatzel are based on (they cannot be missing from any of my 4th gen games either) - my Buizel plush is always right next to me on the computer - along with many of my other sea-otter Pokemon plushies.
My other favorites of course are the feline Pokemon of Sinnoh - Glameow & Purugly, and also Shinx, Luxio, & Luxray. I love cats too.
Some of my other non-weasel, non-cats that I like from Sinnoh are (for me that deserve to get mentioned - as just naming one is almost impossible): Leafeon, Riolu/Lucario, Pachirisu, & Bidoof/Bibarel. [like them based on their design]