I have a few things I like doing it to, moreso than others.

[He pauses for a moment before continuing; you know what, Kira hasn't responded badly to anything he's said so far, so...]

Water and iron is ideal for getting the sort of explosions I want out of it. It leaves an excess of hydrogen in the container, so it builds up pressure instead of just sitting there. It's pretty volatile, just requires being kicked into something.

[...If you get his drift.]