Mini Cooper drivers used to wave at each other in passing. What other ‘communities’ have ways of acknowledging one another that the rest of us are oblivious to?

I expect there may be religious community examples?

Extra tall people?

Those wearing fancy watches?

UPDATE: lots of great car examples but what about non car communities?

UPDATE 2: people ignored update 1 and continued naming car communities but what I’ve learned from this is that there are DOZENS of waves going on between car owners - basically any vehicle that is slightly different qualifies its owners to establish a community. Pleased there’s so much camaraderie out there