Liquid-fuel rocket engines use
regenerative cooling, wherein the cryogenic fuel and/or oxidizer is used to cool the case and nozzle of the engine, and in so doing vaporize the liquid.
Kill two birds with one stone.
In a gas turbine engine, there is a strong thermodynamic case to be made for mid-stage cooling of the compressor airflow. It would not be a pretty picture, with additional air ducts or fuel lines running hither and thither, but it would be a useful way to heat fuel in the tank and simultaneously optimize the engine cycle.
I'm sure it's been considered and rejected because of cost and complexity, but who knows? If fuel approaches $10/gallon, should it be reconsidered?