Bone-conduction headsets.
I only heard about them a while back, but I kinda did think, "Why?" I have a few pairs of wireless ear buds, what's the point?
Now that I have a pair, it's amazing. I didn't know how useful it would be, not to mention just plain cool, to be able to listen to something that nobody else can hear and so doesn't bother them, all while retaining all the sound of the room around me, so that I don't feel disconnected or cut off from the environment like I do with traditional ear buds.
I keep a pair of both at work. Ear buds for video-calls when I want the ambient noise of co-workers blocked out, and the bone conduction set for if I just want music in the background, or I'm doing training videos or youtube or something but still want to hear if somebody is trying to get my attention or just starts talking to me. I take them to the break room during lunch and entertain myself with podcasts, but I don't have to remove anything from my ears when people walk in and talk to me.
I wonder now how I did without them.