WD-40 Use Warning!
If you have an object needing re-lubrication, check to see what sort it presently has before using WD-40. The reason? If the joint or metal part in question is presently lubricated with grease of any sort (white lithium, axle, copper, etc.) then you may be shooting yourself in the foot by using WD-40 because the latter cuts grease. This is why it can be used to clean up bicycle frames. :-) So spraying a greased joint with WD-40 may make things worse very quickly as the remaining design lubricant is cut away by the spray.
To those giggling by this point, you all have sick minds.