I like to buy natural crunchy peanut butter.  And, since it is natural with no additives, the oil and nuts often separate in the jar while it is sitting on the shelf.  This means that in order to use it, the oil and peanuts must be recombined.

At first I used to try to stir them back together.  Unfortunately, the oil often would jump over the side of the jar and create quite a mess.

Finally, I started just shaking the jar instead.  And, to my surprise, it worked quite well.  After about 30 seconds of vigorous shaking, the peanut butter was homogenized, no fuss, no muss.