Life would be boring if you had to limit your creations to the shapes and sizes dictated by mold manufacturers...
With Valentine's Day approaching (or any other special day, actually), interior decoration stores stock their shelves full of vases and other items pertaining to the theme.
This is how, last year, I stumbled upon a glass heart-shaped vase with an angled top and a reversed-tapered body (wider on top than at the bottom). It tickled my imagination so I brought it home.
Then I spent more time than I'm willing to admit to try and find how I could turn it into pillar mold. In the end, it's a simple solution I went with, but one that will allow you to turn pretty much any container into a candle mold.