I have once tried Kimchi Ramune (Korean spicy pickels) and can just tell you not to do that as it tasts awful (found it in Akiba). The other weird thing was Lavender Ramune on a Farm in Furano (Hokkaido) wich was not to bad.
Gotta love that stuff, especially when someone is opening it for the first time
I tried my first in a Izakaya in Tokyo btw.