Snorlax is an excellent sub-puncher, as he has huge HP, good attack, and use outside of subpunching. Another excellent user is Breloom with a very threatening attack stat and the ability to Spore as well as sub. Combine that with his Poison Heal ability, or his lethal Mach Punch and you've got yourself a near-perfect subpuncher, particularly since Talonflame isn't around in Black/White 2. The last one I'm going to mentiond is Hariyama with (again) very high HP and also very high attack, as well as two awesome abilities (although sub kind of works against guts).
Basically you've got the bulky sub, Snorlax,
the powerful subpunch and utility, Breloom,
and the tanky and strong subpunch, Hariyama.
You could of course use any Pokémon with Focus Punch, as almost all Pokémon learn Substitute.