Major Chromatic Players (not specific blues though)

Alder and Reilly were both tongue blockers, though it's likely that both used non-TB techniques when the situation called for it (such as fast, releated staccato notes).

Stevie, nobody knows for sure. He did receive instruction and even played in an adult-directed harmonica band as a child, so he may have been taught tongue blocking. That said, there's no specific evidence of tongue blocking in his playing. he seldom gives inerviews, but he does show up at the NAMM show and walks around playing harmonicas when visiting manufacturers' booths. So maybe if someone could get close, they could ask him.