I did a lime+tequila cream ale last year, it was pretty good. I added the juice of 5 limes, the zest of one lime and about 100ml tequila to 20 litres of beer at the height of fermentation. Personally I felt I could have done with a bit more lime and would increase this next time I do this or try a different variety of lime (like key lime).
I had a pickling lime cream ale one time. It was awful. Dissolved my digestive tract. I am writing this from the grave.