I'm really sorry dress pant sweatpants, but there's only room in my heart for one amazing invention at a time, and you've just been replaced by these brilliant Free Key rings that open with a simple press.
I consider myself a fairly dexterous individual, but I'd rather be tasked with finding Atlantis than putting a new key onto a keyring. At least I know I'd be more successful with the former. But I'm fairly confident I could handle the latter with Eric von Schoultz's Free Key. Its brilliantly simple design just introduces a strategically placed bump in one of the loops, essentially creating a button that can be pressed to open it.
It's another one of those "why weren't they designed like this in the first place?" ideas, and the only thing missing is a set of these in my pocket right now. As far as I can tell they will be available for sale at some point, and I'll be honest, even if they were $US50 a pop I'd still eagerly buy one. [Free Key via Notcot]