[0xTJ]

Arbitrary, not remote, but definitely really cool.

[0x003]

RCE in SMW would be particularly impressive

[patcdr]

I've built a system that kinda does that: https://patcdr.net/carl/listing

tl;dr: People can build ASM modules on that site and load them into my game (when enabled) using chat commands. And it does work on my original SNES by using some SD2SNES trickery.