Regigigas

This is Regigigas; he needs no introduction, as with stats like his, everyone knows that he should be able to do some serious damage. Unfortunately, the biggest letdown with Regigigas is that in order for him to 'do serious damage', he has to survive five turns in battle before his crippling ability, Slow Start, wears off. During those five turns, the opponent almost always either massacres Regigigas or does whatever he or she pleases and phazes him at the last possible moment.

Regigigas isn't all bad news, though, and can actually do something useful in the UU tier, where his raw defensive stats make his survival possible. Base 110 defenses across the board are tough to break, and the general lack of phazers helps Regigigas even more. Once Regigigas has stalled those five turns, he can proceed to crush skulls with his base 160 Attack stat and base 100 Speed stat. While he may not be the prodigal son of legendary Pokemon, Regigigas can certainly hold his own in a tier that isn't used to dealing with Pokemon of his stature.