1. Jump off a cliff
2. Walk under ice and realize that you can't get out and drown.
3.Try to hug a creeper to make it friendly
4. Hug any mob
5. Entering a server [spawn killing]
6. Chopping a tree
7. not paying attention
8. installing 800 mods at once
9. making a fireplace in a treehouse
10. Making a wooden house on a server [griefing]
I had to make an emergency shelter the other day. Dug myself into a cliff side and put dirt at the doorway. Moved a block to see if it was light yet and it looked fine. Dug a little further and a zombie dropped on my head and killed me. That was pretty stupid.