Nominating:
Regirock A- --> A
Let's look at this in terms of ability to perform it's role on a team. Firstly, what is Regirock's role in the current metagame?
- Stealth Rocker
- Sneasel check (SE moves, Thunder Wave, bulky af, Stealth Rock for wittling).
- Physical OR Special wall
- Status spreader/team support
Okay so, looking at Regirock's determined role on a team and the metagame at large, we have to decide whether it fulfils this role to an A grade standard? I for one, would say yes it does, way better than A- grade standard.
Firstly, as its primary role is to set Stealth Rocks, I'd say it's fantastic, and does this to better than A grade standard. It threatens Xatu with rock STAB and stops it from coming in to bounce rocks without being incredibly risky, it's bulk allows it to tank multiple hits and get off rocks I'd say 99% of the time, undeniable A quality in this role.
Second, as a Sneasel check, something that's very necessary on all teams in the current meta. Regirock's primary role already threatens Sneasel's longevity and forces it to have to think twice about coming in just to threaten things out. Regirock's bulk and ability to choose from a wealth of options to take on Sneasel mean it performs this role to perfection, a Choice Band Knock Off isn't a worry as it does 0 to Regirock plus subsequent Knock Off's do even less. Regirock can Drain Punch, T-Wave, Stone Edge, Explosion, Earthquake, all of which Sneasel would just die to, so another A rank quality here.
Third, as a general wall besides Sneasel. Regirock has a great base defense, allowing it to choose between mixed, physical and specially defensive, making it hard to choose what to hit it with during the battle, choose wrong, it can be costly. Specially defensive Regirock acts as a great Magmortar and Pyroar check, and even can tank a hit from Gallade Close Combat and get off a T-Wave/Explosion to knock it out, checking this many threats in the current meta doesn't go unheard of. The status-spreader role is definitely encapsulated in the first three points so I won't go into detail.
Hope you guys agree.