Rather than having an inferior extension where lots of them are registered, I much prefer to have the dot com even if not so many extensions are taken.
Best one I have is probably 1066 .com with 52 extensions taken
I am not going to name my most popular but i want to break it down.
Most low balls.
Most enquired.
Most traffic landed.
Most search value cpc vs exact search.
Mostly your own click.