One way to have a wedding that everyone will always remember is to have it on a date that everyone will always remember. A date like 11-12-13 comes to mind.
There are any number of other things you can do to have memorable nuptials.
Have an Ice Wedding:
Almost any extraordinary setting will do for an extraordinary wedding. Why not have you wedding in an ice hotel?
Have a Green Wedding
Given the number of people who are talking a green game, you might want to have a green wedding just to show you can walk the walk!
Sweet Sticky Rainbow Wedding
Think of it as a cartoon wedding. All gumdrop and lollipops. All rainbows and moonbeams. Incense and peppermints. Unicorns and dandy lions.
Militant Milk Mustache Wedding
This is an invitation to have a wild wedding. It could be anything from the bride and groom going commando to having you and a priest jump out of a perfectly good airplane and recite your vows as the grounds comes up at 120 mph. There's the underwater wedding. The bungee jumping wedding. The hot air balloon wedding...