The ones generall recognised to be the best are McHugh's (Killester/Artane, just before the Artane Roundabout on the Malahide Rd, and Kilbarrack, on the Kilbarrack Rd just before it hits the coast road) and Redmonds in Ranelagh.
Martin's Off-Licence on Fairview has a small but lovely stock of beers - I've seen one or two there that McHugh's don't have, but otherwise I think they use the same distributors. However, what they do have at the moment, that McHugh's haven't had for a couple of years now is Well's Banana Bread Beer, probably my stable English ale. It's lovely. It's *not* a fruit beer, not sweet at all, a proper bitter, but made with bananas at some point, so has a wonderful, nutty aroma of fresh-baked banana bread.