Do you mean beers as in proper beers? Or does that include Lagers/Bitters/Ales, etc.
For me, my favourite Bitter is Boddingtons; favourute Lager is Cobra, with Fosters Gold a close second.
As for real Beers, I'm actually going through a phase of trying a different one everytime I go to Tesco/Asda/Sainsbury's. So I'm keen to here people's recommendations on what I should try next?