Totally unexpected and happy surprise was a big pile of beautifully preserved pillow basalt, clearly defined alteration rims around them, and opalized amygdules. This was cause for a whoop and a screeching halt to go play!
Not even remotely unexpected in the desert are mudcracks. But I liked seeing them anyway.
Neither expected or unexpected, this was a very white bug. It's standing on vesicular basalt, by the way.