Kenda Kross plus 1.9 x 26inch, smooth in the middle with knobs on the sides. I've put 500 miles on mine and they show little wear, good traction on road, good enough off pavment except for mud and steep climbs. Very easy rolling, big improvment over my knobbies- pump them both to 65psi. $11 each at my LBS I couldn't afford a road bike so I went with these. Some urban mtb riders are using totally smooth tires for more traction when playing in parking garages, I couldn't say what brands though. And he may like the look of some knobs on the sides over no knobs or vise versa, but the straight line performance is the same.
Get some lightweight tubes and put half(2oz) the recomended(4oz) amount of Slime sealant in the tubes and squish it around by hand to make sure its well coated, if you try to gently squeeze the slime into the tube it will clog, you must give the bottle a sharp hard squeeze. My tires have held their pressure for 9 months since adding slime without topping off. Every ride I've ever gone on without useing either tough skins or slime I've had a flat, but have never had a flat when using either(over 15 years). And the weight isn't noticable, at half rate its 2oz/56g [light MTB tubes weigh around 125g, standards are about 150g, 'tuff' tubes are 200-300g]. All of the tires at this site look pretty good to me, most even have a higher pressure rating than mine but I would go with 1.5-2.0 width not the 1.3 or 1.4. A wider tire at the same pressure as a skinny tire will have greater load capacity and lower rolling resistance but pressure ratings tend to go down as tires get wider, in this catagory its a toss up so go med to wide for handling reasons.
http://www.biketiresdirect.com/slicks.htm