Seven himself in the franchise, to the point where he has countless tributes and even sequels and remakes dedicated only to him. He's practically the poster child of the franchise along with the original Ultraman.
Hell Is That Noise: Alien Bell emits a high-pitched ringing sound that humans can't stand, but it can stun Seven.
Alien Guts' roar.
King Joe's mechanical sound.
Either the radar ping or the actual (not audible to humans) sound when the Ghos aliens arrived on Earth caused Dan pain.
Part of the setup for Episode 39 (a daytime patrol by two Ultra Garrison members that came up with nothing but a happy scene at an amusement park full of unsuspecting people), compared to what happened after Dan and Anne run into the Guts aliens...
The was a hilarious moment in Episode 24 "Return North!" when the Kanan aliens, operating out of a lighthouse, place Windam under their control, causing him to attack Dan. Dan transforms and "defeats" his friend by wearing him down, complete with "Fight! Ultraseven" playing in the background. This happens just as Furuhashi has a close call with an airliner.
Soundtrack Dissonance: Tense moments in Episode 8, as well as the Tear Jerker end of Episode 12, are scored to upbeat, classical-sounding, music.
Uncanny Valley: The featureless aliens in "Seek Tomorrow" wear masks with blank eyes (think Batman in the comics) and unmovable mouths (like Michael Myers).