I'm thinking of creating my own mod for Minecraft, while following
Pahimar's most excellent Let's Mod series. Having played with a few of the FTB packs (Mindcrack, Beta, Direwolf20, and Ultimate), I've noticed that steam doesn't get a lot of love. Yeah, Railcraft has boilers and steam, but using them for anything is painfully inefficient, not to mention a fair bit inelegant with all but the snazziest of setups.
So, my solution? A steampunk-themed mod inspired by Thief! I wanna use something kinda resembling how real-life steam works, you have the boilers which have to have water and such to keep running, with steam lines and such, BUT...you need to keep an eye on your pressure levels, which will be conveniently handled by gauges (steampunk isn't steampunk without gauges!) that you can place on steam lines or boilers to give you a visual indication of the pressure (in PSI) in a given steam system. Steam system being defined as either a boiler or a network of contiguous pipes and any machines to which they're connected.
What would happen if you overpressurize a system, with no emergency release (also craftable, attaches to either a boiler or steam pipe)? Depends on what you're talkin about, but in general, things explode. A standard iron boiler would likely end up with roughly the power of half a block of dynamite, whereas an industrial-grade boiler would explode with the force of 4 blocks of dynamite, and the other grades and types will scale between the two. If its pipes that are overpressurized, a random pipe on the system will be chosen, and it'll blow up, but while it won't do any structural damage (this may change, depending on pipe grade), any living things nearby will take a pretty large hit from the boiling-hot steam and shrapnel.
But! Its not all steam, after all, Thief isn't all technology. There's some magic, as well, and I've always been fond of well-done magitech. One thing I plan on making is steam golems. They're similar to iron golems, but require more in the way of resources, have a bit less health, but will hit much harder. Now that I think about it...I wonder how cool it'd be to have a golem that would be able to build a building off blueprints. Just mark a chest (or other inventory) for them to draw from, give them a blueprint to work with, and they'll set to building! Hell, maybe work in something to where you can have more than one working on the same building project, as a team...