Giant SCR2.0 - takes guards, and tyres up to 25C/26C
I ride 25s in poor weather (using the DA22 wheels that came on the bike) and 23s in good weather (ha ha) using a set of Mavic Aksium wheels I got 2nd hand from Mortiroloboy of this parish.
FWIW, I think full guards (as opposed to clip ons) are the way to go if you're serious about riding year round.