Here's a fun and easy little stove. It's made from this bottle from Walmart (or wherever):
To make it I made a couple cuts to take a center section out, popped out the spray mechanism, drilled a few side holes, then inverted the top and inserted it into the base.
Here's a picture of the flame pattern and the stove from a couple diff't perspectives:
If I was going to do it again, I'd definitely make it a bit smaller, and I'd add a few more holes. Right now there are 16.