Apple: You can service it with a wooden stick

Direct from the Apple Service Guide for a PowerMac

Screw a cup hook into the center of the remaining rivet and holding onto the hook, rock the rivet back and forth until you work it out of the heatsink cover. Note: You may find it useful to insert a wooden stick into the hook to help pull out the rivet.

Yeah, they suggest you use a "wooden stick" while servicing the computer.