I want one new block type, and I'm not even sure why I want it. But if it exists, I must have it.
Basically, a block that you can 'swim' through like water, but doesn't flow or fall and can be placed like a normal block. I have an urge to make some midair waterways like in Ecco: The Tides of Time.
--
"I'm Commander Shepard, and you're standing in the biggest library in Citadel Space. Look me up."