One dinner conversation I had a revolutionary idea. The same scent glands in dogs are in human's underarms. What would happen in a dystopian future where people marked their territory with their armpits.
You would have situations such as a neighbor watering their lawn, when suddenly a rambunctious juvenile runs up and marks the neighbors tree with their arm. Furiously the neighbor shouts as the juvenile runs away.
Instead of dog fights, their would be shouting matches. Two men in suits shout at each other during an evening promenade because one of them marked the others fire hydrant.
And for greetings people would sniff each others armpit just to identify the person with the smell.
If you liked your neighbors Mustang, you could slide up and mark their car with your unique odor.
What makes the most sense about this is that of all your senses, you remember smells the best.