Some of those are beautiful.
I remember having one of those, way back in my memory somewhere, but I must have forgotten to leave it to myself in my various wills because I don't have it anymore.

Any of these ways would be great to bump off unwanted political figures, but I think we'd need something untraceable really. Unless Gordon Brown really is so unpopular the police wouldn't even bother to investigate.
Personally I love the shark idea, but that's just because I'm blood thirsty and bored.