I chose Bismuth because of its usefulness in the alloys that are used to reduce need for lead-based products (lead is considered by many to be significantly toxic), not to mention its crystallized (oxidized) structures are one of the most beautiful things I've seen (up close and online, since it's actually safe to touch).
I have to say Technetium. It was the first synthetic element, it can be used in nuclear medicine and fission, and it looks and sounds cool.