As Kelvin said, Crib Goch, Tryfan North Ridge and Bristly Ridge are all do-able in the wet. Another wet weather option is the False Gribin-Y Gribin Ridge route though it's just an easy grade 1 scramble. If you want a bit more excitement, the grade 2 routes on the Idwal Slabs are also possible in damp conditions, though I'd give them a miss if the rock is too wet.