A more challenging variation of "use the last letter".
User posts a Pokemon (i.e. Voltorb), the next user posts a Pokemon beginning with the last letter (i.e. Bulbasaur).
See if we can mention 'em all! (What is it now, 650 of them?).
EDIT: Here's a nice little chart to keep up with the progress, make things more interesting, maybe. Sorry there're no names and numbers on it but I couldn't find a decent chart that had those. I'll be updating it regularly and maybe we'll just catch 'em all. Also, you can get a better look by copying the image URL and looking it up.
(so far we've covered all Pokemon beginning with E, I, N, O, R, U, X and Y)
Oh no, I mean Oddish
Hoppip! You cute pokemon yooooou :3
Umbreon *Cough*The best Eveelution*cough*
Man, E has got to be one of the most uncommon first letters when it comes to Pokemon.
(we've got a nice Pokérap going on now)
Sudowoodo or however it is you spell that, I'm fairly sure it starts on S and ends in O though.