An unexpected excess of snot deposited on your finger. Not to be confused with the Surprise blow, which could be omitted from genitalia or assorted other orifices!
You're pretty sure your nose just has a tiny wee booger in there. You breach the outer rim slightly and strike gold straight away. It's not even crusty.. & you're not even feeling clogged up!
You extract your finger to find a nasal snot baby attached to your finger the size of a cherry!!
WOAH! Where did THAT come from?? That's the surprise pick!