I have been trying to make an effective team to face Genga with and I decided to do a trick room team, so here goes nothing.
Banette - Lead - Focus Sash
EVs: 252 HP, 252 Attack
Nature: Brave
Ability: Cursed Body
Moves:
Taunt (Stops opponent from setting up)
Destiny Bond (Take the foe down with me)
Shadow Claw (STAB)
Trick Room (I think we all know why)
Rampardos - Physical Sweeper - Choice Band
EVs: 252 Attack, 252 HP
Nature: Brave
Ability: Mold Breaker
Moves:
Head Smash/Stone Edge (STAB either way)
Earthquake (Coverage)
Zen Headbutt (Coverage)
Hammer Arm (More coverage
Gardevoir - Support - Lum Berry
EVs: 252 Sp.defense, 252 Sp.attack
Nature: Quiet
Ability: Trace/Synchronize?
Moves:
Wish (HP regain)
Trick Room (No need to Explain)
Shadow Ball (Coverage)
Psychic (STAB)
Zangoose - Physical Sweeper - Toxic Orb
EVs: 252 Attack, 252 HP
Nature: Brave
Ability: Toxic Boost
Moves:
Facade (STAB, lots of damage with toxic boost and doubled power and STAB)
Close Combat (Coverage)
Night Slash (Coverage)
X-Scissor (Coverage)
Exeggutor - Specia Support - Wide Lens
EVs: 252 Sp.Attack, 252 HP
Nature: Quiet
Ability: Harvest
Moves:
Trick Room (You get it)
Sleep Powder (Helps him operate, boosted accuracy thanks to wide lens)
Psychic (STAB)
Leech Seed (Nothing to say here)
Absol - Another Physical Sweeper - Razor Claw
EVs: 252 Attack, 252 HP
Nature: Brave
Ability: Super Luck
Moves:
Swords Dance (attack boosts for sweeping)
Perish Song (Usually Forces a switch, enemy pays for it if they don't switch)
Psycho Cut (Coverage, 50% of critical hit)
Night Slash (STAB, 50% chance of critical hit)