This isn't a Legacy post, but Mirage Mirror and Torment of Hailfire are definitely the tits in EDH. Torment can just wipe out everyone at once with enough mana and Mirror gets you whatever is the most broken permanent on the board at the time.

Mirror is also surprisingly resilient, since it can copy other permanent types to avoid whatever removal is aimed at it if the opponent fires at it in Mirror mode. Could see that as being a strong point in Legacy, since it can dodge Abrupt Decay, Grudge, etc.

Torment also did feel powerful for a punisher card, strong enough that there weren't enough good outs when cast. I could see that making it into some Legacy deck.