I'm new to minecraft and got interested in it from watching youtube videos my fiance watched. Sooooo I guess my most newbie death was when I first started playing and the first night came. I was busy building a small house when something green started coming towards me. I was all 'awwwwww so cute' and walked right up to it..........then the creeper blew me and my house up.
When I first got minecraft I was afraid of squids....... I thought the squids were attacking me because I was drowing and I didn't know how to swim, so I thought the squids were hostile. Also, I didn't know how to make a roof on my little dirt shack.....
Installing a texture pack by replacing the texture files in my .jar with the texture pack ones. This then permanently left me with that texture pack. Trying to fix it, I deleted my .minecraft and lost my first, and best, world.
That I know how you feel. When I had only had minecraft for a few weeks, about the time that ocelots were added minecraft crashed and my only two worlds were deleted
Also, on the creative world, I discovered TNT and didn't know how to ignite it, so I used lava.