Using noise removal plugs such as RX or XNoise as sound design tools rather than for noise removal.

For example, take a longish, constant waveform that has some variation in it dynamically like a backhoe digging a ditch. By either using extreme settings or swapping over to difference monitoring you can create some very unique source material with a little experimentation. Great for making ambiences.

When I'm out field recording I will often just leave the Sound Devices rolling in between real takes to capture the random sounds of the next setup just for the purposes of having lots of unique source to use this technique with.