Some planets in the universe are tidally locked with their stars. This means that their rotation speed is the same as their orbit, so one side is always facing its star, and the other is always facing away from its star. Because of this, one side of the planet will always be scolding hot, while the other side will always freezing. However, there is a small section in the middle where the temperature is perfect, water can be a liquid, and normal life can be sustained. I think it would be nice if we had planets where one half was volcanic and the other half was frozen, but the middle would be forest. It would look something like this: Also, the volcanic side would always be daytime and the freezing side would always be nighttime. So, the sun would only move when you walk around.
I don't think the scolding side would be molten, as that would require volcanic planet-side activity. Maybe just a really hot desert. Otherwise, cool idea.
If one side of a planet is always facing it's star, the star would melt that side of the planet and create magma.
This is a great suggestion. Right in line with the kind of suggestions I've been wanting to make for more realistic (but awesome) planet types in the universe. It should be possible to simply turn off the night/ day cycle on certain planets, but I'm not sure how much work would have to go into it for them to make the nice habitable biome appear right at the two locations where night meets day. I suspect it is doable, just more complicated then randomly generating the biome locations. Very good suggestion though.
It would probably all have to be the same since it is the same planet. Otherwise they would have to completely change the way they do the difficulty programming.