Well, I have an idea, but not a song. I guess you'd call it a rhyme. You know when people say 'I'm rubber, you're glue. Whatever you say bounces off of me and sticks to you'. That'd work really well for Wobbuffet, due to it's extensive use of Counter & Mirror Coat.
Edit: Some others I didn't have time to put in last night-
Raichu- Supercharger by Machine Head. This could work for lots of electric types, really. Raichu's pokedex entry says it can charge up to 100000 volts, so that fits well. Lyric: "...crushing the competition in their tracks. 100,000 Volts we blast...".
Metagross- Indestructible by Disturbed. This could work for any super-strong pokemon, but Metagross' steel type makes it the best fit. Lyric: "Every broken enemy will know that their opponent had to be invincible. Take a last look around while you're alive. I'm an indestructible master of war"
Tyranitar/Metagross- Bulldozer by Machine Head. Tyranitar is said to move mountains when on a rampage, and Metagross, like a bulldozer, is made of steel. Lyric: "Bulldozer feeds upon the weaker as they fall. Bulldozer crushes all."