Not necessarily a whole block, but a sort of imaginary pressure. It could be used in the creation of volcanoes and water spouts. It's essentially a block that reverses gravity, causing liquid to flow upward if it's above it. It would be a map-generated block, therefore it couldn't be used by players, as it isn't mineable.
A geyser holding up a block of diamond. Win.
Now I like this idea.
Once the geyser's down, the block goes down too.
I would have jack-o-lantern geysers.
Nozzle block?
Im guessing pretty much liek a controlable geyser block.
Just search it, you'll see what I mean.