Priority, any scarfer at Chomp's speed or faster, any weather sweeper, Hail/Sand, Toxic Spikes, Deo-S, Double Chop Garchomp (or any other outspeeding multiattacker), or any Roar/Whirlwind phazer that doesn't fear an unboosted hit (or any phazer that can take a boosted hit, if any such exists)...