ie. Keeled over, Croaked, kicked the bucket
you get the idea
I’ve always suspected that “red shirted” (left on the sidelines) should have a more profound meaning for Trekkies. 
There’s always the old “Gone to the great <fill in the blank> in the sky.”
You know – cowboys go to the great roundup in the sky, teachers to the great schoolhouse in the sky, software engineers go to the great Unix platform in the sky, etc.
(Software engineers sent to the great Windows platform in the sky should get used to the scent of sulfur.)
Passed over, gone to the next realm
“Checking out of the system”
Shuffled off this mortal coil. Bought the farm. Pushing up daisies. Feeding the worms.
At least according to Terry Pratchett.
go to a better place, pass away, receive one’s final reward, to keel over, to pass on, to expire, to perish, to succumb, to bite the dust
Dirt Nap is my personal fave.
‘E’s not pinin’! 'E’s passed on! This parrot is no more! He has ceased to be! 'E’s expired and gone to meet 'is maker! 'E’s a stiff! Bereft of life, 'e rests in peace! If you hadn’t nailed 'im to the perch 'e’d be pushing up the daisies! 'Is metabolic processes are now 'istory! 'E’s off the twig! 'E’s kicked the bucket, 'e’s shuffled off ‘is mortal coil, run down the curtain and joined the bleedin’ choir invisibile!! THIS IS AN EX-PARROT!!
If you don’t recognize this, look here: http://www.serve.com/bonzai/monty/classics/ThePetShopSketch-1
Bought the farm
Breathed his last breath
Feeding the worms/fishes
Gone to his reward
Departed
The Big Sleep
Riding the sod sidecar
And of course …
Gone home.
Crossed the river Jordan.
Gone to be with Jesus.
Mort, according to Piers Anthony.
visiting Davy Jones Locker
And if you suddenly end up in a Star Trek universe, with a red shirt on, it’s safe to panic. Unless someone calls you a rank above Lt. Then you’re probably a guest star at least, and safe. Possibly immortal.
From Cecil…
Shakiong hands with Jesus
others
getting pissed in heaven
drving that big ole cloud car
living with our relatives in MO
Taking a road trip with Thelma and Louise
“went tits up”
“gave up the ghost”
“pushing up daisies”
**Cashed his check
Bumped up
Forwarded to the postoffice in the sky
Went to the happy hunting ground
Lost his pulse for good
Found peace at last
Assume room temperature.
Bite the big one.
The big sleep.
Bobbing for earthworms.