-Must be hard difficulty
You make a new game and start gathering as much wood, food and armor as you can. You can only gather the things on the surface until the beginning of the 2nd night (2nd time the sun sets).
Once the sun sets the second time, you must dig downwards as far as you can go. Once you hit either bedrock or a big cave you must explore. You cannot go back to the surface until all your wood is used up. Everything else you will need will be underground.
The only real problem with this play style (or possibly the best thing about it) is that it is conceivable to live forever underground without running out of supplies.
While on the surface during the first two days grab some saplings and some wheat seeds. Then once you secure a base deep underground you can build a wheat farm and a tree farm (dirt is plentiful down there, don't bring any with), providing wood and food forever.
Then as long as you don't die from other causes you should be able to survive indefinitely underground.
This isn't an original idea on my part (see here) but I've tried it and it is fun. Pack up some basics, pick a direction and start walking... Shelter each night in a cave and do a little mining, smelting and crafting for the next day.
Once you're away from your spawn point it is pretty much iron man since you are going to lose everything you've done when you die. I've found I get really cowardly after a couple of days :smile.gif:
One tip: glass is your friend for walling yourself in at night. You want to see when it is dawn, and be able to see any mobs waiting for you.
Some of the scenery is really spectacular. Still haven't found my natural outside lava-fall yet though...
Yeah, I thought up that idea independently myself shortly after I started playing. My idea was to just head east, towards the rising sun all day every day, just chopping the occasional tree or mining some cobble and coal along the way. Then I saw someone was doing a video so I figured I would just watch them do it instead. :wink.gif:
Oh, and the first map I ever played I spawned looking directly at a mountain with an external waterfall and lava fall coming from it. Sorry.