When they let me apply for my personalized license plate, they let you pick 5 just in case the others get denied. My choices in order were: RE1GN, YO, NAH, FRIEND and IKUZO. Although "YO" wasn't my first choice, it's actually grown on me a lot more and I'm glad that I ended up with this over my first decision.
Not only is it one of the few two letter words in English, the numerous times I've seen people say "yo" to their friends and point as I drive by is pretty awesome. I'm definitely planning on keeping this license plate for any future cars.
Also, in BC, we are unfortunately only limited to 6 letters or numbers on our license plates which really restricts what you can put on there.