1) Children. When people are like "Look what my kid learned to do yesterday!" and the kid claps, I'm not impressed. Of course your child learned to clap, it's developmentally appropriate for your child to learn to clap right now. Unless your child is a prodigy and actually does some thing out of the norm, I'm not impressed.
2) Cars/Motorcycles. As far as I'm concerned, the purpose of vehicles is to transport people and stuff from one point to another. So when people (mostly men) rev their engines and have those cars/motorcycles that make so much noise, I not only don't feel impressed I feel annoyed. You're not just wasting gas, you're producing noise pollution. Pollution doesn't impress me.
3) Money. When people show off their money buying and flaunting expensive things, I'm not impressed, in fact I feel insulted. I have three jobs and I'm still (what most Americans would constitute as) poor. When people buy expensive watches, watches that cost more than what I make in a year, it feels like a slap in the face. I'm a teacher, so I don't make a lot of money. I've always known that teachers make 'little' money. So when people spend so much on inanimate objects that won't make them happy, my frivolous teacher brain is unimpressed.
4) Guitar strumming. Guitar is a great instrument, and I am impressed by people who can read music (not tab) and play said music on the guitar. Guitar's also great because it's an instrument that many people can pick up and somewhat teach themselves. But when they learn only how to strum, I'm disappointed. It's limiting the guitar which is capable of so much more than block chords. When people only halfway learn the guitar, I'm not impressed.
5) Smoking. It's no secret that smoking (anything) is bad for you. It doesn't have any health benefits. When people start to smoke it baffles me. You know it's bad for you and addictive, yet you still started? There must be something wrong with you or you must have a death and ugly wish. It doesn't make you look cool, it makes you look dumb for wasting your money and body on something that has nothing good to offer you. Also, it smells terrible and can kill others through second hand smoking. So thanks for the cancer, you unimpressive person.
I'll leave you with this song.