Bet you can't guess how this instrument received its name?! (Hint: Look at it!) While the triangle looks deceivingly simple to play (which, for the most part, it is), it is also capable of producing many sounds. One fun thing to experiment with is to try and determine which side of the instrument "sounds best." Of course, there is no correct answer although most triangles do have one side that most people will recognize (and agree upon) as having the "best' sound" based upon their subjective responses.
When purchasing a triangle, as with all musical instruments, it's best to try it out before spending your hard-earned dollars. Don't buy the cheapest available as you'll get what you pay for - and triangles DO sound different depending upon their quality. I bought the above instrument about twenty years ago for approximately $15 and have never regretted it.