Negative temperature
It might seem absurd, but things at negative temperatures are actually hotter than things at positive temperatures (above absolute zero). If something with a negative temperature comes in contact with a positive-temperature object, heat will go from the negative object to the positive. This is because temperature is a trade-off between energy and entropy. If you add energy to a positive-temperature object, it will increase in entropy. If you add energy to a negative-temperature object, it will decrease in entropy.