Candle Adhesive
There is nothing I hate more than a wobbly candle in it's holder. How it tips back and forth in the cup everytime there's a little vibration.
It's just a fire hazard that is going to become a real blaze in a matter of time, but this is the stuff I swear by to make it all a little better.
Use a pea-size portion on the candle's base, shove it in the holder and give it a light twist. It never hardens and can wash off with hot soapy water.
The container it comes in is approx. 2.25 inches in diameter by 1 inch tall.