Start with a sweeter cake flavour such as the raspberry/white chocolate and honeycomb or pecan/maple and follow up with a zesty/citrus flavour such as the lemon or lime/coconut milk/passionfruit. Finish on the two chocolates.
Some notes on the flavours;
3 flavours if you are having a 4 tier cake or 2 flavours if you are having a 3 tier cake. This will provide an equal(ish) amount of each flavour. Each cake tier will have 4 layers of cake and 3 layers of fillings, so there is plenty of flavour running though the portion. It is always nice to have contrasting flavours and from experience the guys tend to like the chocolatey, sweet flavours and the ladies the fruity, zesty cakes.