Poor Regirock. It has 0 votes. Like, none. Zilch, Nada, Cero.
So in honor of Regirock, I'm unofficially changing my vote, even though I voted for Registeel.
Regirock is actually pretty freaking cool. Sure, Regice and Registeel are actual golems with brains and organs and everything, but just look at this entry from FR/LG.
"It is entirely composed of rocks with no sign of a brain or heart. It is a mystery even to modern scientists."
Whoa. That's pretty cool, even for a Pokemon. But that's not all, it also is self-repairing. What is this thing, a prehistoric automaton???? I mean seriously, only Porygon MAYBE comes close to the craziness of this thing. But Porygon isn't as cool as a Legendary Golem.
Then there's the actual base stats, which gets more into competitive battling. Regirock has a Base Defense of 200(!) which makes it an undeniable tank. It's crazy in it's defenses. Regice on the other hand, has 200 Sp. Def, but has weaknesses like Fighting, Rock, and Steel, which are mostly all Attack, not Sp. Attack, so Regice is at quite a big loss. And while Registeel is the more balanced and versatile option, it's Attack is lower than Regirock. Lower, I tell ya. So Regirock is suddenly the best tank AND the best mixed attacker. Definitely a force to be reckoned with.
On to specific attacks. While each Regi has a decent moveset and learns the H. Beam at 65, Regice and Regirock are the best attackers, so let's look at them. Both move pools are VERY similar except for the fact that Regirock has Iron Defense, boosting its already unbreakable Defense with MORE Defense. Regice just has some Amnesia, but hey, it's not my fault when you get OHKO'd with a Arm Thrust on Regice and I can laugh it off on Regirock.
So there you all have it. While Regice and Registeel are undoubtedly very awesome, don't forget about this hidden titan, also tucked away in the crevices of Pokemon. Because really, all those thousands of years of sandstorms have toughened up Regirock to be a beast. And if we're looking at design, I'd like to point out that Regirock lacks fingers. He doesn't need them; he just fists you in the face.
Awesome.