I'm not sure about future ATP level, but definitely Samuel Groth (Jarmila's ex). The guy's serve is just lethal.
I think he's currently at Futures level, though, after injuries.
Probably the only guy that serves as hard as Taylor Dent did. I remember him hitting consecutive serves close to 150mph, and not the Ivo Karlovic ones, real hammers measured accordingly ... but lethal?
He barely made half of serves in, and his second looked quite common to me, don't think that can hold well at ATP level.