Spoon
Take a spoon in your dominant hand, and hold the jar in the other hand. Now, wedge the spoon head in the gap between the jar and the lid, in such a way that, the concave surface is facing towards you. Make sure that you have firmly gripped the jar. Now, push the spoon head towards the jar for a second, and then pull it towards you. Repeat the same at different positions on the lid. The jar will be open in a few attempts.