Rock is in one of the greatest physical shapes of his life.
He looks great, but his most recent matches have been atrociously slow, with almost 2 minutes of 'both men down' for every 5 minutes of wrestling. The fact that even Punk couldn't have a good match with a guy who used to be a great worker speaks volumes. Unfortunately, today's Rock is as rusty as it gets, which is a shame because he was a serious GOAT candidate in his day.
I actually think that one last HHH/Rock match, booked properly, would be a great Rock swan song. Rock really should have beaten HHH at WrestleMania 2000 (and he did beat him at Backlash in a much better match, but c'mon, it's Backlash) and I'd like to see Rock get his receipt.
That said, Rock also had a big loss to Brock and if the Rock/Brock rumors are true, I think it would be a great use of both part-timers to do that match, since they can come and go as they please and it wouldn't interfere with anyone else's storyline.
Other than that, Cena/Rock is played played out, Punk/Rock's kinda the same away (and Rock doesn't need to lose to Punk since he already lost to Cena). I can't think of anyone else. Don't care to see Sheamus, Orton, or Big Show face The Rock.
Rock/HHH? I like that, they should go down that road at WM30 & then please for the love of God - retire both of you.