What it does
Extrasensory is a Psychic-type special move with a chance to make the target flinch (skip its turn). The flinch only matters if you move first — if the target already acted, the flinch does nothing since the turn already resolved.
Psychic coverage is valuable against Fighting and Poison types, and relatively few defensive types resist it. Middling base power with a potential bonus flinch — solid but not spectacular on its own.
In doubles, the flinch is single-target only. The classic pairing: a teammate uses Fake Out on one opposing Pokémon while your Extrasensory user targets the other, hoping the flinch lands on the second one. If both connect with their effects, neither opposing Pokémon acts that turn.
Who runs it
Roserade at 50% treats it as a core slot. High Special Attack, Speed 90, and Psychic coverage lets it threaten Fighting-types that would otherwise wall its Poison-type attacks. The flinch chance is a bonus on top of consistent damage output.
Greninja at 16% demonstrates the speed interaction most clearly. At base Speed 122, it's going first against almost everything, which means the flinch chance is live on almost every Extrasensory it fires. That combination — reliable speed, solid damage, flinch chance — makes the move genuinely threatening.
Typhlosion at 12% uses it as coverage, particularly against Fighting-types that fire-type moves don't hit well.
How to use it
Flinch requires going first. Before clicking Extrasensory, confirm your Speed advantage over the target. Against slower targets, the flinch is a real possibility. Against faster ones, you just have a Psychic-type damage move.
In doubles, don't build a whole turn around 'the flinch will land.' Treat it as a damage tool with a bonus. If it flinches, great — your partner gets a free action. If it doesn't, you still dealt damage.
Tips & strategy
Extrasensory hits Special Defense; Psyshock hits Physical Defense despite being a special move. Check your target: if it has low Physical Defense and high Special Defense (many Fighting-types fit this profile), Psyshock may deal more damage. Extrasensory stays better against high-Sp.Def targets. Neither move is universally superior — it depends on the matchup.