Water cool a human.
Obviously humans are already liquid cooled, but you could enhance this further. Custom "blocks" (or something, this would be the hardest part of the build, but I can think of a few ways to do it) attached to the person at key areas (eg: back of neck and wrists, under arms, etc), then you pump the water through some radiators that are either separate or as part of a backpack.
Phase 2 OTT version: use colder water.
Does this make any sort of sense? No, you can just put your feet in cold water and your body will cool down quickly.
Is it totally awesome though? I reckon, yeah.
