Big man Japan (2007)
Chosen by me as it was offered free online
An odd, melancholy movie. This did the internet rounds a few years back for it's bizarre CGI fight sequences and baffling obtuse monsters (a head on a leg bounces around for some reason).
Shot for the most part in docu style and not immediately obvious as to what it is about (we hear the lead talk a lot about liking things that grow big on command before seeing his power).
It may stretch it's point of the main character being a sad pathetic loner a little too much but is an affecting and interesting take on Godzilla tropes.
It's ending (after the 'hero' kills his Grandad whilst running away from a bizarre Demon thing) is utterly mind boggling. Switching from CGI to trad. man in suit trashing cardboard city shenanigans it may have a political point to score (something about North Korea and the USA maybe?) but fucked if I know. It plays out strange Ultraman pastiche that highlights the casual brutality of a lot of children's entertainment (they really lay into the poor monster/man in suit) that is clever and both funny and horrifying at the same time.
There's not much else out there quite like it - that's for sure.