Choker

Noun

 * 1) A piece of jewelry or ornamental fabric, worn as a necklace, tight to the throat.
 * 2) One who, or that which, chokes or strangles.
 * 3) One who operates the choke of an engine during ignition.
 * 4)  Any disappointing or upsetting circumstance.

Synonyms

 * (one who chokes another): strangler
 * (slang: disappointing or upsetting circumstance): bummer, downer, pisser