I've become a slave to Zipp Tangentes, both the open tubulars 
(a realtively silly name for "clincher"
) and thew tubulars, which I race on. 
 
They are oh so smooth riding, good puncture resistance, low-ish rolling resistance. I like 'em. 
 
Footnote: Man, I've tried a lot of different tires: 
 
-Michelin Pro Race 3 
(quite nice
). 
-Continental Attack and Force combination 
(my second favorite
). 
-Continental Gran Prix 4000 
(pretty good, nothing to write home about, just good tires...
) 
-Continental Gran Prix 4000 "S" 
(nope, couldn;t tell the difference with the "S"
) 
-Vittoria Pro Slick 
(ride nice, but flat quite easily, low mileage tire
). 
-Vittoria Rubino 
(better than pro slick
). 
-Vittoria Rubino Pro Tech 
(very nice, like the continentals mostly
). 
-Vittoria Open Corsa CX 
(super, super nice ride but not-so-good durability
).