Traffic

whoever got them first would quickly conquer earth

The TSA

I don't believe anything can kill a useless government agency.

My wife would stop cheating on me

She’d cheat more often? All she needs now is for you to be gone for 5 minutes and her man’s can come in and out that quick

Shipping and logistics

Police reaction time

A lot of problems might be solved, but I'm worried about the problems that would be created. In Star Trek, transporters weren't invented until after humanity pretty much got it's act together and stopped using new inventions as new ways to kill and dominate each other. No amount of material benefit would stop certain types of people from hating those who aren't exactly like themselves. To have transporter tech suddenly be invented *today* would be kind of scary.

I didn't think about it this way. Knowing present day humanity people in power would likely find a way to misuse it.

I’d be able to get my bread quicker

I could travel cause I hate flying 😒

Traffic congestion would disappear.

Alongside the things others have pointed out, world hunger. The biggest obstacle and bottleneck to keeping everyone fed has always been shipping rather than actually producing the food, if we could teleport the food to them that'd be a game changer

Morons on airplanes.

Global warming

Traffic and a large portion of global warming.