Bontrager CX0
size: 700x38, about 37 mm wide. Also available in 700x34
tread pattern: small knobs in center, larger knobs on the edge
construction: 120 tpi
performance on pavement: excellent, very fast tire
performance on firm gravel: excellent
performance on deep or soft gravel: very good. Just OK in mud though.
durability: below average. Mine are almost completely bald in the center after ~2500 miles. Above average flats.
ride: smooth and fast
Panaracer/Pacenti Pari-Moto
size: 650x38, about 37 mm wide. Also available in 650x42
tread pattern: smooth, just a light herringbone
construction: 120 tpi
performance on pavement: excellent, very fast tire
performance on firm gravel: excellent
performance on deep or soft gravel: good; wide/supple enough to float on top of most surfaces. No tread, so no good for mud.
durability: Surprisingly, above average. Only 2 flats in ~2000 miles.
ride: plush and very fast
Compass Stampede Pass
size: 700x32, about 31 mm wide.
tread pattern: smooth, just a light herringbone
construction: 120 tpi
performance on pavement: excellent, very fast tire
performance on firm gravel: very good
performance on deep or soft gravel: Just OK, not wide enough to float. No tread, so no good for mud.
durability: Only ~50 miles in, so no report.
ride: very fast
Panaracer Gravel King SK
size: 700x32, about 32 mm wide.
tread pattern: small 1 mm square knobs
construction: 120 tpi
performance on pavement: good, fast tire
performance on firm gravel: excellent
performance on deep or soft gravel: Good, not wide enough to float. Decent tread.
durability: Only ~50 miles in, so no report.
ride: fast. The mini-knobs make it ride a tiny bit slower than a smooth tire, but make it much more confident in gravel.
Schwalbe Thunder Burt (Evo Liteskin)
size: 26"x54, about 52 mm wide. Also available in 27.5" and 29" diameters, in 54 and 57 mm widths, and with different casings/protection/tubeless.
tread pattern: small 2 mm square knobs, larger edge knobs
construction: 120 tpi
performance on pavement: good, fast for its size but a little squishy in hard turns (that's what you get at ~35 psi)
performance on firm gravel: excellent
performance on deep or soft gravel: excellent, plenty of float.
durability: Only ~100 miles in, so no report.
ride: fast. The mini-knobs give it good enough traction for occasional mud, but it's still a very fast tire for its width.
The Thunder Burt is one of the most popular tires for Dirty Kanza because it has good width and traction but not much rolling resistance.
I concur with others regarding the Challenge Gravel Grinder Race tires; I've ridden them a little bit and they seem great.
They're going back on my gravel bike after 'cross season. I put on Challenge Limus Pro Open tires for the couple cyclocross races I'm doing.