The slippery equivalent of duct tape. An aerosol lubricant in a fetching blue and yellow can that, in the words of its label:

Stops sqeaks * Protects Metal * Loosens Rusted Parts *Frees Sticky Mechanisms *

Listen up, kids. If you have nothing else in your nifty tool kit, you'll pack WD-40. After nearly reducing my co-workers to writhing, gibbering idiots with a squeaky desk chair, a hastily purchased can was the only thing that stood between me and an inter-office cannibal massacre. As a young and chronically foolish children, my brother and I also found it made an excellent flame-thrower. (NOTE: this is in no way an endorsement of self-destructive or pyromaniacal behaviour. Use at own risk!)

Also from the label:
DO NOT use in the presence of open flame or spark. Keep can away from electrical current or battery terminals. Disconnect electrical tools and applications before spraying.
DO NOT place in hot water or near radiators, stoves or other sources of heat.
DO NOT puncture or incinerate container or store at temperatures over 50 degrees Celcius. DO NOT puncture, crush or incinerate (burn) can, even when empty. VENTILATION: Use under well ventilated conditions.
FIRST AID TREATMENT: Contains petroleum distillates. If swallowed, call physician or poison control centre immediately. KEEP OUT OF REACH OF CHILDREN