Seymour puts up an aggressive fight against Audrey II, and dies diving into the plant with a machete in the hopes of hacking it apart from the inside. That image of Seymour fearlessly staring down Audrey II's mouth is truly a badass way to go out.
Right before Orin reaches his last breath:
Orin: What'd I ever do to you? Seymour: Nothing. It's what you did to her.
Yes, he (it?) was the villain of the movie, but c'mon, admit it...Audrey II's final number ("Mean Green Mother From Outer Space) in the 1986 musical version of Little Shop of Horrors was easily the greatest friggin' part of the entire movie. So great, the song was nominated for an Oscar. If you don't believe me, watch for yourself.