Levonorgestrel
"I've never had kids, and read all the horror reviews before going for my appt.
Truth is: Yes it was super uncomfortable. The clamp felt like a period cramp that wouldn't ebb off. It was not 'painful', and definitely not the worst pain I've ever been in. If you've stubbed your toe or had your ears pierced, you will be just fine. 
I held the nurse assistants hand which really helped (silly I know) and I talked about something else the whole way through to keep distracted.
Please don't let the 'insertion torture' reviews put you off having the IUD. Everyone is different, and it's unlikely you will be one of the people who has an awful experience. I drove there and home myself and was fine."