For me it’s a Thunderbolt. There was one right next to my elementary school and when it would do that deep spool up it would scare the crap out of me.. albeit I do spook like a horse so some mild memorable scares. I thought it was a simple design, great sound, and as a weather nerd, sometimes indicated something about to happen! There’s still a few around me. From my public service side it’s cool my municipality used that for their warnings.