My worst experience was swallowing a battery when I was 7, (don't ask how it happened I don't remember it too clearly myself) all I remember was going to the hospital to get it X-rayed. but it was great to brag about it too my friends afterwards. How I would so causally swallow a battery, and how was I was the big hard guy in the class because I survived this.
(In reality, I remember screaming after swallowing it, and thinking I was going to die, I was 7, and I freaked out a little)
All in all a bad experience, but one I could tell my friends afterwards, and I won't go into detail about how the battery came out, but eventually it did.