Froslass

Although Froslass seems outclassed by Deoxys-S, it has a few traits that differentiate it from the cosmic biped. Firstly, Froslass is the only Pokemon in the game that can both spinblock and use Spikes. Secondly, Froslass is immune to Extreme Speed, the most common priority move in the tier. This allows it to almost always get two turns against slower opponents--of which there are many, thanks to Froslass's base 110 Speed stat. Lastly, Froslass's ability, Cursed Body, allows it to disable moves from Choice Pokemon and render mono-attackers useless. However, Froslass is still extraordinarily frail and weak, suffering the dilemma of having to choose between using Taunt or setting up hazards; the wrong choice can let an opponent knock it out or set up on it.