One girl with amazing skills that's inching closer and closer to having absolutely no gag reflex is Sarah Vandella - see her amazing work in "Suck It Dry #7". She goes balls deep on about an 8" cock (it's on the thinner side girth-wise, but it's still fairly large), holds it there for seconds at a stretch, and even winks at the camera at one point in that position. Truly balls-draining!
There are other girls that are very good - Sisi Sinz, Angelina Valentine and Tara Lynn Foxx come to mind - but they're not totally gag-free. Tara is taking thicker 8"-9" black cocks down her throat on a regular basis now - one example is in "Black Cock Addiction #7" - but still gags as the last few inches go into her esophagus.
There are plenty of newer girls that have real promise or have shown some great skillz at points - Rachel Milan (in "Throat Jobs #7"), Jasmine Jolie, Missy Mae
Historically, Bobbi Bliss and Jeanna Fine were absolute masters of the gag-less deepthroat. Bobbi Bliss in "I Swallow" (#1 or #2 - I'm not sure which) took two HUGE black cocks all the way down over and over with no percievable gag - just insanely hot.
I'm sure others will chime in with their favorites.
[Personally speaking, I love any girl getting throated - gagging or no - but that's me...]
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