Can't believe I missed this topic. Square or hex(ish) are the only ones, I also have a soft spot for the oblong fairchilds and such like - guess they look omega ish. Drivers I have eventually come to the conclusion suck but my first real life exposure was the adidas one............
Come to think of it that wasn't so bad, bought for ?25 and sold within a week for ?85 :D Round ones must be harvested and then forgotton about.
Aside - for those with very young children ONLY WEAR JEFF'S M1. It's vomit proof as I found out yesterday and it shuts crying babies up when you're stuck with them in the back of the car WAH WAH WAH.....oh pretty blue light. 15 minutes I had to press that button - god knows what it's done to the battery life but oh the peace........bliss