"Howdy" for me. I'm from and live in the Northeast.

Started saying it ironically on work calls to break up the monotony of saying "Hey" when the host joined the meeting and said hello. It was pretty much just a joke at first. Now it's about 50% of what I say in response to someone joining the meeting saying hello.

Honestly, I kind of like it. It's folksy, friendly, simple, and informal. It's slipped out a couple of times when guests arrive at a family party and are walking in the door and saying their hellos, but it's mostly relegated to work meetings.

A few of my coworkers have even started doing it occasionally, so it seems like it's catching on.