Multi-Battling
Doubles will give you a lot of potential, but don't use EQ if your Partner can't take that hit (use Drill Run instead there). If you can get away with EQ past your partner (such as with Air Balloon, Flying Type, Levitate Ability, or Magnet Rise), smash away. Just make sure your opponent isn't using such tactics, too.
Triples show a ton of potential for Exca' to wreak havoc. EQ and Rock Slide have great potential and many of its usual partners are bulky in HP, defenses, or both and have ways around Sandstorm damage.
Note that opponent teams with Magnet Pull Ability and Wide Guard will prevent half of Exca's usual offense and lock you if you go Choice.
Notable partners in Doubles/Triples (due to Sandstorm and EQ immunities) include Cloud Nine-taria, Magic Guard Sigilyph, Overcoat Mandibuzz, Skarmory, Flygon, Levitate Bronzong, Claydol, Solrock, Lunatone, Gliscor, Archeops, and Landorus. I do NOT recommend Aerodactyl unless Exca and Aero are on the sides in Triples because of Pressure.
If you can block Surf, Rock Types and Exca will have a huge advantage. Wide Guard on your side is great for that reason, especially if you can block Sandstorm Damage (Carracosta, Swampert, Torterra, and Bastiodon are quite adept at it, as are Throh, Alomomola, Hariyama, and Conkeldurr with Leftovers).
Blocking EQ and Sandstorm with Leftovers/Black Sludge and Levitate gives a few more options. Gengar and Weezing can fill the Black Sludge niche, while Mismagius, Carnivine, Rotom, and Eelektross can fill the Levitate-Leftovers role.