Trick Room could become very powerful. One of its main limitations has been switching from setters to abusers; it takes a turn, and could lead to your TR abuser getting smashed in the switch.
A Linked Trick Room / U-turn combo could be very good here; the u-turn is guaranteed to go last, and you get potentially twice as many moves to use while under TR. This beats non-priority protect / fake out, but is stalled out by priority protect / fake out.
I love Trick Room, so I wanted to find some 'mons that could abuse this combo. It looks like Fake Out is really dominant, so here are three sets that beat it, albeit without U-turn, sadly (no Ghost/Inner Focus user learns it and Trick Room).
Dusclops @ Eviolite
Ability: Frisk
EVs: 252 HP / 70 Def / 188 SpD
Bold Nature
IVs: 0 Atk / 0 Spe
- Trick Room
- Memento
- (Filler)
- (Filler)
Dusclops is bulky enough to take most hits and setup Trick Room, then proceed to sacrifice itself while crippling the opponent in the meantime. Memento will allow you to safely bring in a setup sweeper, and will often negate any boosts the enemy thinks it can set up on Dusclops. If you're worried about Taunt, Mental Herb Cofagrigus can run the same set with similar levels of bulk. One nice thing about Dusclops, however, is that Frisk can scout the enemy lead's item.
Gourgeist-Super @ Sitrus Berry/Normal Gem
Ability: Frisk
EVs: 252 HP / 252 Atk / 4 Def
Brave Nature
IVs: 0 Spe
- Trick Room
- Explosion
- (Filler)
- (Filler)
Another Frisk-using suicidal Ghost? Gourgeist is a more offensive variant of the above set, with worse bulk and arguably worse typing, but the ability to deal massive damage with Explosion. Sitrus Berry lets you live more hits, but Normal Gem boosts the power of Explosion. Gourgeist is also more effective to keep around before you set up Trick Room and die, as it can throw out Leech Seed and do good priority damage with Shadow Sneak, among other options. Still, it's primary goal is to allow a slow sweeper 5 turns of Trick Room, and possibly kill weak Pokemon not expecting Explosion.
Girafarig @ Sitrus Berry/Leftovers
Ability: Inner Focus
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Trick Room
- Baton Pass
- Future Sight/Psychic
- Calm Mind/Nasty Plot/Hyper Voice
The only Inner Focus user that I can find with a switch move, Girafarig is the only one of these three sets that actually lives when it sets up Trick Room, allowing it to come back and do it again. Baton Pass will always go last, ensuring a safe switch. Girafarig is sadly quite frail, so it can't afford to mix its defensive stats or hold an offensive item/Mental Herb. The last two slots are if you're feeling cheeky -- if you can manage to safely use Future Sight before you Baton Pass out, your TR client will enjoy a bonus chunk of damage when they attack. You could also set up a Calm Mind or Nasty Plot to pass along with TR. If you just want reliable, weak, poorly-covered damage, Psychic and Hyper Voice are always options.