The best players that I know of are: Trex, Revan, Okazaki aka ESFn00b, twigsnapper (I have no clue who this actually is) and Sub - in no particular order. I know Sailent is good but I've only seen him play once and I've yet to see anything from Ice-X. I honestly believe Trex is the best ESF player in America but he didn't particpate in the tournament. I wish this tournament would proceed to some degree so I could put the fights up on youtube and show people some of the top tier players at the moment.
@ Renyori's comment; There may be many scripters currently - I honestly couldn't tell you but from my time of being active within the 1.2.3 community I've come acrossed, seemingly, all pros with many years of experience. 1.2.3 doesn't have that many players but I know that on Sundays there are get togethers, like an unofficial 1v1 tournament mostly run by werty and trex if I'm not mistaken.