What have the Celts ever done for us?

This famous Monty Python clip tells us everything we need to know about the way the Roman Empire and Roman civilization has been viewed down the present day. But recent archaelogical evidence, and new theories, are making us rethink our attitudes to the Romans. Were they always more civilized than the people they conquered, or were they just very good at stealing other people's ideas? Should we be asking, "What did the Celts ever do for us?" Because it turns out they were ahead of the Romans in many ways. A few of which, I'll investigate here: I'm thinking feminism, roads, chariot suspension, chain mail, stabbing swords, telegraph systems, celestial navigation and accurate calendars to mention but a few.