I have choked twice, and it was NOT pleasant.
The worst time, I was eating dinner with those I lived with at the youth hostel, I was about 16 - I laughed, and a bit of food got stuck.
I couldn't breathe, I was gasping for air, it hurt SO badly. It felt like eternity, but I reckon it was minutes.
They had to do the Heimlich manoeuvre on me, or I would've literally choked to death, very quickly.
After I could breathe, it took quite some time for me to feel ok again. Fuck, it was horrible. It was pretty traumatic.
The most painful thing EVER, and the scariest. Even if you tried it on yourself, your survival instinct would kick in, in an instant. Trust me. Horrific way to go