Angel_Mapper has released CTF-PhaseShift, a unique map featuring morning and evening parallel worlds... and ghosts. The ghosts are actually the ghostly mirrored shapes of players in the other "world". It certainly gives a twist to your average CTF map.
To the right is a screenshot of the evening world. There are more screenshots (including the ghosts) in this thread. You can pick up the 10MB file here.
Update - hal(2:48AM EST 11/21/03) There is an updated file that fixes the bot problems in the original version.