What's your favorite Guinea Pig film?

It's hard to deny the iconicity in the disturbing/exploitation movie scene of the Guinea Pig series, and deservingly so. They're bizarre, they're all so different and varied from each other, and mostly made by different filmmakers. You can always feel that no matter how gross and weird and sometimes darkly hilarious whatever is happening on screen is, the people behind the scenes were just trying their best to make a fun little fucked up ride for us to enjoy. What's your favorite in the series?

Mine is absolutely Mermaid In A Manhole. It's one of my favorite films of all time. Its so weird and nasty, and strangely, for whats usually a low brow series, really well written. I absolutely adore it. I'm not going to spoil anything because it has a pretty good twist. If you haven't seen it, go watch it!