Seven's transformation sequences, especially the full-length version (as in Episode 4).
When Alien Bell incapacitated Dan with its signature sound, Dan just waved his arms in front of his chest and transformed without the benefit of the Ultra Eye.
The Ultra Garrison's Big Damn Heroes moment in Episode 40 when they used the Magma Raider to rescue Seven.
Seven's attack in Episode 22, with the Ultra Garrison's help.
How about "ULTRA SEVEN", the Gratuitous English other theme song of the series? This troper especially loves the version done by Isao Sasaki in the Ultraseven Evolution series.