I was thinking about the Mummy ability, and how useless it seemed. I mean, sure you can take out the ability of an opponent, but then I realized… since that opponent then has the same ability, you could switch in soemthing that has a crappy ability and have it negated yourself.
Could work wonders on Slaking and Regigigas.
Get an opponent infected with Mummy, switch, and then hit them with a priority move (or Pursuit) off of either Slaking or Regigigas. A little gimmicky, but it could work.