I think it's got to be some Saint Agur, or some Gorgonzola for me, although Stilton and Brie are very close behind!
Most cheese is good, but i'm not a fan of ones like crumbly Lancashire or Wensleydale... i'll eat cheddar 'til the cows come home though, it's so moreish :)
Can't forget the pickled onions to accompany the cheese and crackers either, love them things!