Originally Posted by MikeWMass

I use KMC links. I find that the first time or two they are tough to undo. If you flex the chain so that the link is horizontal and the two ends of the chain are hanging down (looks like a Stonehenge monument, I'm too lazy to take a picture and upload), you can use whatever pliers you like to squeeze it open, you don't have to buy the Park tool or grind down a pair of needlenose pliers.