Andrew Maxwell is definitely the best of the Irish at the moment, although Dara O'Briain is consistently good, specially live. I mean really consistently. I saw him twice in one night last year and he was brilliant both times! :D
Also Karl Spain is hilarious just as a straight stand up, especially when in front of an English audience.
Love Frankie Boyle in stand up and Mock the Week too. F**ker will say anything!
And Steve Hughes also brilliant. "I was an angry young man, but you've got to eat." :D
Rather than rehash more names that have been posted before, many of which are top notch (but Eddie Murphy?? Seriously???!!!), some of the best lesser known acts that ye should definitely check out if you haven't already include Michael McEntyre, Simon Evans, Rhod Gilbert, Mark Watson, Reginald D Hunter, We Are Klang, Stewart Francis, Glenn Wool, and the brilliant Ben Bailey.