Inexpensive, low-end paint with a bright, round shell that will not break in your barrel or chamber. Unfortunately, these balls will not reliably break on any target that is not rock hard.
Monster Balls Paintballs
Monster Balls are inexpensive, readily available and work better than many other discount brands of paint, but do not compare to high-end paint. If price is your primary concern, Monster Balls are not a bad choice.