But, having been impressed and amused by other people's icons, I'm starting to make some of my own, so here's one I'm going to use for SF (whether my own writing or talking about books/films/TV shows).
It's taken from this sign, which always amuses me whenever I pass it -- which is currently once a week. I've been meaning to stop and take a picture for ages, but couldn't get organised to set off early enough with the camera in order to do it. The sign is just outside Llangollen, a small North Wales town famous for the International Eisteddfod and the Doctor Who museum. I love the dalek where there would normally be an elephant (for zoo) or house symbol (for stately home).
The picture isn't as good as it could be. I couldn't take the photo square on because the sun was right behind the sign. If I ever pass that way later in the day, I'll stop and re-do it. That's assuming it remains there for much longer. On Googling to find a web page for the Dr Who Experience, I've just discovered that the exhibition closed last summer. So don't all rush there to see it or you'll be sadly disappointed.