A Gimmick would be a technical advantage, despite the Pokemon's stats being so low.
It can either be a move, an ability, or a stat. Like how both Wobuffet and Pykamuku have laughable offensive stats, but are insane tanks and can take any hit.
Shedinja's wonderguard, which allows it's HP to be 1, without risking much in terms of viability due to the circumstance.
Ditto's transform, which in gen V, became Imposter.