i have yet to lose a big one (knock on wood) but small fish in good shape get frozen (ive ended up with quite the collection) ones that have benn partially eaten by tankmates are flushed
I throw small ones into the neighbor's yard. Raccoons, cats or whatever take care of them for me.
I used to freeze big ones and just collect them if they were pretty. Then I got married and no more freezer fish for me.
I toss dead fish from my pond over a hill for the raccoons and cats to eat; fish in aquariums either get fed to my pond fish, turtle, or ducks or get flushed, depending on size and cause of death.
me and my gf hold a military-style funeral/ceremony at my fav. lake, blow the "canned-horn", place the fish on a leaf (most fish 10lbs and under will fit on the giant elephant leaves we got here) and float it out to the center of the pond. there are some huge catfish in the lake and we wait until the fish gets either sucked under by one of them or sinks to the bottom when the leaf gives out.
at this point, i used to dispense a round from my .22 into the air until my gf and i watched "1000 ways to die". now i just pop a firecracker and we give the salute.
this only happends with my intended aquarium fish though. feeders are just thrown into the lake and given some respect too (im a selective softy). all will end up as food for another fish/crustacean in one way, shape or form.
but prior to the funeral, once the fish dies we freeze it in a zip-lock "body bag" until we can make time for it. im planning a funeral right now for my clown knife. ... this guy was my first fatality by way of mistake. his death will not be in vein...
Flush small ones, and when the times comes I'll probably bury the big ones....or freeze them and show them off when I wan't to pretend I caught them while fishing.