The best beer is always the one that fits the situation best.
In pubs, most of the time a refreshing continental lager, like a Cronenbourg, Grolsch, Becks Vier or the like. In the summer/when it's hot & at BBQ, I like either the lighter, american style beers (e.g. Corrs, stuff that isn't even real beer for some people), or the German Weissbier/Hefeweizen, when it's available. In Winter with dinner sometimes the heavier, darker Belgium style (Leffe) ones, or the German Pils. And with Mexican food it has to be Corona or St Miguel!