Undoubtedly the least expensive computer gaming accessory I have bought in a while is a little USB powered fan I found in a local discount store.
It's getting warmer in my attic man-cave. But my large oscillating fan is a little too noisy and a little to strong so I end up turning it on, then off, then on again and so on. This little fan provides a gentle flow of air which I can aim directly at me without it being too much. It's also very quiet and runs on power from the computer's USB port.
It's Chinese made and unbranded and only cost a few pounds. Bargain!