The opening theme. Takayuki Miyauchi's voice is powerful.
Growing the Beard: The series begins with a much lighter and goofier tone than its predecessor (Kamen Rider Black was probably the darkest instalment of the franchise in the 20th century)—jarringly so. The arc beginning in episode 14, however, features more tense, serious storytelling throughout, peaking in episode 15, with Kotaro achieving his new Super Mode while screaming in rage with a dead child cradled in his arms. The series doesn't forget its comedic side after the arc concludes, but it does learn to balance comedy and drama better.
Never Live It Down: Even though Shadow Moon eventually did a Heel–Face Turn here, he's usually remembered as a "Kickass Kamen Rider villain", thus he usually gets villain roles in other works featuring Black and RX.
To the point that, in the first Kamen Rider Decade movie, an alternate Shadow Moon is the Big Bad, and it takes a mass Rider Kick performed by every title Rider from the original through Decade to finish him off.
Values Dissonance: Episode 13 is going to make public viewings a little awkward, with naked Hitomi (who's like six) and her dad in the bath.