Excadrill

Singles Sets
Excadrill @ Life Orb / Choice Band / Focus Sash
4 HP / 252 Atk / 252 Spe
nature: Adamant
ability: Sand Rush
- Earthquake
- Rock Slide
- Swords Dance / X-Scissor
- Return

• Earthquake and Rock Slide have great coverage together, while Return hits Pokemon that can take both attacks such as Virizion and Rotom-W for decent damage, OHKOing after a Swords Dance boost.
• Since Excadrill may not have the chance to get up a Swords Dance boost due to the fast nature of GBU singles play, Choice Band is an alternative over Life Orb, to dish out as much damage as possible at once. Focus Sash is a tertiary option to allow Excadrill to always take an attack, beating down common checks such as Gliscor or Conkeldurr.
• Conkeldurr and Gliscor both take Excadrill down easily, so a strong special attacker such as Latios or Reuniclus can make an excellent partner for Excadrill. Skarmory easily phazes it out, so Magnezone or a Pokemon such as Heatran that can set up on Skarmory can work well.

Doubles/Triples Sets
Excadrill @ Focus Sash / Chople Berry / Earth Gem
4 HP / 252 Atk / 252 Spe
nature: Adamant
ability: Sand Rush
- Earthquake / Drill Run
- Rock Slide
- X-Scissor
- Protect

• Earthquake and Rock Slide have excellent coverage together. X-Scissor allows Excadrill to 3HKO Cresselia and 2HKO Latios and Latias. Drill Run only hits a single target, but doesn't hit Excadrill's partner, allowing Excadrill to be used alongside Tyranitar or Hippowdon without necessitating an Air Balloon.
• Focus Sash allows Excadrill to take any attack despite its many weaknesses and hit back hard, but Chople Berry lets it take Hitmontop's Fake Out and Mach Punch, unlike Focus Sash. An Earth Gem boost the powerof Earthquake or Drill Run for one use, which can be gamebreaking if used correctly.

I see Focus Sash used quite often in singles. I hate this thing.

I think Drill Run is worth a mention on Doubles Excadrill. I often see it paired up with Tyranitar in the team's vanguard, and since many people prefer Chople Berry to Air Balloon on Tyranitar (Since the foe knows you're probably going to bring T-tar out in the beginning, they'll most likely use their Fighting-type at hand to beat it quickly, and having Excadrill on the team too means they're even more likely to include it) it is used in place of Earthquake sometimes. It hits the one foe a little harder than Earthquake after STAB and the reduction to 75% damage for area attacks (120 damage versus 112) and compensates for its 5% accuracy difference with a heightened critical hit ratio. If you feel you'll often be in situations where either your ally will not be able to nullify Earthquake or one of the foes will be immune to (or at least take minimal damage from) Earthquake, Drill Run is useful.

Yeah it's definitely an alternate option and with both Sandstream abusers being hit by Earthquake, it can be quite useful.