Gin Fizz (Gin, lemonjuice, sugar and soda) is shaken, where as Tom Collins is
stirred, and contains a little less soda.
I think B52 was originally made with Grand Marnier, but if you want to
substitute GM with cointreau (or the Kahlua with Tia Maria) all you do is
alter the taste slightly. Where I am from it is more common to serve it with
kahlua, baileys and Cointreau. Try different variations, and see which one you
like.