Rats!

rats

An exclamation of frustration, disappointment, or vexation. Oh, rats—I dropped another screw. A: "Sorry, I won't be able to come this Saturday." B: "Rats! OK, we'll try to get together some other time."
See also: rat
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

Rats!

exclam. Oh, damn! Rats! I broke a nail!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
See also:
References in classic literature ?
"Trained rats!" Manuel Fonseca, the contortionist, exploded in the bar-room of the Hotel Annandale, after refusing to drink with Duckworth.
Poor rats! They seem only to exist so that cats and dogs may gain credit for killing them and chemists make a fortune by inventing specialties in poison for their destruction.
But the rats! they swam the river, they gnawed their way through the thick stone walls, and ate him alive where he sat.
I am the rat-catcher!...Let me pass, with my rats!..."
"You dirty rats!" Jimmy Cagney walking down Buffalo Avenue.
Footsteps pounded behind us, and I heard someone yell, "Come back, you dirty rats!" At that moment, I stepped onto the sensor mat in front of the automatic sliding doors.