In an answer to this question, the brilliant diagram below was given:
The chart makes chilled ethylene look like a very appealing choice, yet I don't believe it is ever used. Why not?
Edit: I just checked the wonderful "Ignition" by John D Clark and while ethylene oxide and many other compounds are mentioned ethylene gets only one mention:
Alcohol, ammonia, and JP-4 or RP-I were the fuels usually burned with LOX, but practically every other inflammable liquid available has been tried experimentally at one time or another. RMI tried, for instance, cyclopropane, ethylene, methyl acetylene, and methyl amine. None of these was any particular improvement on the usual fuels.
(this was around 1950 and their concern was mainly missile boosters, not upper stages).