dumbfuck: used against people when they're being idiotic at the most obvious things. Can also be used when you're happy and surprised about something or someone .
"Example 1: "YOU DUMBFUCK THATS NOT HOW YOU OPEN A PEPSI CAN
Example 2: "OH MY GODD YOU DUMBFUCKK THANK YOU SO MUCH FOR THIS! I CANT BELIEVE IT.
"Example 3: " YOU STUPID IDOTIC DUMBFUCK THAT WAS MY SISTER YOU RAN OVER