I LOVE the buildup. The girl stands there in front of a cheering crowd knowing what is about to happen to her. I love to study her reaction which almost always includes some kind of nervousness (hand fidgeting, brushing back her hair, ect). Sometimes there's that look on her face which says "I can't believe I'm letting you do this to me." In this situation guys usually just try to brace themselves and look as cool as possible given the situation. Girls show their emotions more with more giggling in general. The differences in reaction probably have a lot to do with biological differences between men and women. I like to see the girl stand there while the pie is right there in front of her ready to be thrown. The idea of a guy doing this to a girl is also a turn on, because guys traditionally were taught to treat girls with respect.
If I'm at a mud volleyball event I also like the buildup. You have this deep, gooey oozing mud pit and then some really neat clean girls come and stand next to it. I love the idea that they have PREPARED to get dirty, bringing towel, change of cloths, ect. I love to look at their clean bodies as they stand next to the mud pit because of the inevitability of what is about to happen...