My roadified MTB has 26 x 1 1/8 Conti Gatorskins.
I'm not sure that tyre is still available, but it is terribly good for an MTB used on the road.
I run them booth at 80 psi and find them grippy, responsive and fairly fast on tarmac.
I like the fattish profil for rolling into corners in a more 'MTB' style.
I think if I went for a really thin tyre I'd lose something of the front-end feel these give me.