In that case, I would burn all my money rather than pay it in taxes before I died. Just put every single penny you have into Bitcoin or something and then purposely delete the private keys.
Because I don't really know of any charities that I would support, but I could support some sort of open source software, I guess, like donate everything to fdroid, or something.
FOSS related: The Free Software Foundation, The Software Freedom Conservency, The Software Freedom Law Center, the Electronic Frontier Foundation (aka the EFF), Debian, the Mozilla Foundation, the Document Foundation (aka Libreoffice)...