In reply to tmawer:
All three of the classic E2s at Houghton are utterly brilliant (Mandarin, Rhododendron Buttress and Boadicea) and make a memorable day out.
Having done all those more familiar, great grit E2s that have been mentioned already, and those that haven't (Regent Street, Billy Whizz, Knightsbridge, Quietus, etc.), I'd agree that Mandarin is right up there and hard to beat.
(PS: for Jon - Houghton is not a typical Lancs hole in the ground. The faces are huge, and it has an amazing "Lost World" feel to it, where you might almost expect a Veloceraptor to jump out of the undergrowth...).