Just thought of somewhat of a idea Rope that you can use by attaching to a surface with a pin and lower self down into areas with a key, Example you know thos big holes in the map well sets say you put a pin in the ground right beside it and then press "E" n it, ok then walk into the hole you fall maybe a foot in till the default rope length is used up then by holding a key lets say "L" for lower it will slowly lower you down. once you hit the bottom you could touch the rope with "E" and the rope will detach it's self from you and hang there. Then when your done you grab the rope again and Raise self up with lets say the "R" key to the edge till you can just see the pin in the ground and by pressing "E" it puts you back on the ground where the pin is (since you can't grab edges).
I just thought of this idea now so any better ways to run this post a comment
Some cool use's
Exploring Caves
Secret areas in Dungeons on can get to with this or building a block stairs for a long time
Explore "Hell" - Yah that's right I seen it down there 
Get down from steep cliff
if being chased by monster find a hole and lower self and wait till it goes away...unless they will fly then your probably screwed
Something similar was planned in the very early days: a grappling hook, which can be thrown (for example to get out of a cave when it is too steep). I think it makes a lot of sense to combine these two things, i.e. on the one hand, you can throw the grappling hook, but on the other hand, you can also place it directly at the spot where you are (as you described). I hope we can implement it soon!
