I'm not going to peek either! But here are my guesses for the finale:
Michael says, "Did I come on Bachelor Pad to find a wife? No..." then says, "But I fell in love anyway!" Then does some romantic gesture to Rachel like a stupid proposal or something.
I'm going to guess that Rachel is upset because she and Nick win, but he chooses to keep the $250K for himself instead of sharing it, so she winds up with nothing. HA!
Maybe the shocker is Kalon and Lindzi getting engaged?
I know my guesses are pretty far-fetched, but I'm trying to go against what the producers are trying to get us to believe based on the previews.