I've got a couple of favorite variations on adding things to beer. I used to work in a microbrewery (in the US) and we had an ice cream shop next door. We used to drop a scoop of ice cream into a pint of stout and make stout floats. The contrast of sweet and bitter, with a creamy taste throughout, was lovely (even better when it was raspberry stout season).

In Mexico, and especially in Mexico City, they make a drink called a michelada, which is very light Mexican beer (Corona, Sol, etc.) poured into a frosted glass, in which is some crushed ice and lime juice, and with a salted rim. Sounds a bit odd, but it's really perfect on a hot, hot day.