I recently read an article about a mile hurdle relay that was done back in the 1970s (http://hepstrack.com/blog/2011/04/25/stuff-my-dad-did/). People have posted in the comments about other unique relays, like the 24 hour mile relay and a recent 1600m shuttle hurdle relay done at EIU.
What are some other unique relays that people have witnessed/participated in? After all, this is Relays week.