Simile: "Useless as..."

…a trombone in a gunfight.

Unless I missed it, I’m surprised no one has said Useless as tits on a nun, or balls on a priest.

…as a one armed paper-hanger.

You missed it.

Another vote for

tits on a boar hog
minor nitpick, it really should be teats on a boar hog

but everyone says tits.

YOU’RE AS USELESS AS…

Sandals on an amputee

A resume on a hobo

Whitney Houston’s sponsor

Anna Nicole Smith at a spelling bee

Clay Aiken in a whorehouse

Lindsay Lohan’s dinner

An ashtray on a crotch rocket

A snooze button on a smoke alarm

As useless as…

Anne Frank’s drum kit
A football bat
A pedal powered wheelchair

If someone with a broke dick hears you say that their feelings being hurt are probably the least of their concerns.