STP

These are all clinchers:

For mud racing: Michelin Mud (green)
For dry racing: Continental Cyclocross Speed (although I'm still looking around because I don't find them quite adequate)
For all rounder gravel/commute: Maxxis Mud Wrestler

I used Ritchey Speedmax's for a while and found them much more suitable for commuting and gravel trails, but not for racing, especially in wet grass or snow. That's just me, though. Others will have different opinions.

eddubal

-Hardpack/dry: Kenda Small Block Eights (Don't use for mud)
-Mud: I'm about to try out the Michelin Mud 2s They got good reviews from both press and populace.
-Commuting/onroad: Gatorskins (28) They are a little on the heavy side, but work well.

fietsbob

had durable WTB Allterrainasaurus on for a while. tread in blocks,
even if tight pattern , absorbs energy on the road, moving as it rolls.
still got barely any wear on them..

Jack Brown 33.3 tires made by Panasonic. slick light and low rolling resistance
Durability less important, rubber on tread is thin. ...
Their Pasela tourguard is much more durable ..

as you say , Another bike with the Schwalbe Marathon +'s
gets the daily use..

kennykaos

tubular?race wheels:challenge fangos in 34
clincher/training:hutchison bulldogs

contango 

Mine has the Specialized Borough CX tyres that it came with. So far they've survived London's roads (and presumably the odd pass over broken glass etc, since I'm used to indestructible Schwalbe Marathon tyres on my MTB) and a few excursions over gravel etc. From what I hear they aren't all that great so I'm considering putting Marathon Extremes on it.

I've used an Extreme on the back of my MTB for the best part of 1000 miles, including a 150-mile ride in two days and 110 miles in one day. It holds up fine, has never let me down. It can be quite loud at speed (over about 10mph and people around you will notice it, over about 20mph and you'll notice it, although if you go over about 30mph you stop noticing it because the wind noise drowns it out)

I forget if they come in 700x38 or 700x40, but either way they'll be narrower than the 26x2.0 I've got on the MTB.

stevemtbr

Panaracer T Serve in a 28 for road and dirt road use. Schwable Racing Ralph in a 35 for cross training and more aggressive off road riding. Ritchey Speed Max Pro in a 32 for racing.

Ramjm_2000

Commute: Vittoria Rondi Pros 32s
Race: Used to run Tufos now bulldogs

mgurtzweiler

Commuter/Rain/Ride with the wife bike: 37mm Schwalbe Supreme @ 45psi or so

Training Tire: 23mm Gatorskin Hardshell. Going to up that to 25mm once these wear out.

Racing (road): My favorite tire has been Schwalbe Ultremo ZX have not flatted in a race yet but EVERY time I get lazy and just do a training ride on them I flat... Guess that's the difference between riding on the road in a race and on the shoulder on a training ride.

I commuted on the non-hardshell Gatorskins for a couple years and would get around 3000-4000 miles before the flats started to happen. Overall nice tires.

RT

A strong vote here for Specialized Nimbus. High psi and duuuuurable.

eddubal

My CX bike just became KIA, so I've been running my vintage MTB for training. I'm running 26" wheels and have been using the Schwalbe CX Pro Sport 26" with some good results. They do also come in 700c too. The only drawback is cornering on asphalt. It gets a little mushy (probably from the high profile corner knobs). Otherwise, it's been good in the grass, dirt, and mud that I've been working out in.

Eclectus

I've installed Schwalbe Dureme 32s. On-road usage, lots of not-so-good maintenance, some icky tire-punturing debris. Very good riding in the past 4 months, Kansas (shiit!), Monterey/Pebble Beach, SF, Napa/Sonoma.

FormerBMX'er

Only a few cross races on me, but I like the feel and grip of WTB Cross Wolf.

c_m_shooter

Panarager Tourguard 32mm for road and light trail. Either Schwalbe Marathon Extreme 45mm or Bontranger 1.8" for rough singletrack.