On the one hand, Zangoose can really rip any Ghosts a new one with its Fury Cutter attack, and it can slash through other types as well. Seviper is powerful enough to hang on long enough to use the Venoshock+Toxic Spikes combo, AND keep STAB with it.
On the other hand, Mawile is Steel, which is awesome. It's really good if it's Baton Passed in with high stats, and gains the power to rip through opponents. Sableye has absolutely no weaknesses, which is very useful, and can take the opponent's strategy and shove it up their nearest orfice. Painfully.
I choose Mawile+Sableye, just because I love pissing off the opposition more than I like simply bulling through them.