Pea gravel

Pros
  • Durable
  • Can be power washed
  • Can be acid washed
  • Attractive (to some people)
  • Inexpensive ($5.75 per square foot from my builder in the Houston area)
  • Extremely slip-resistant
  • Supposedly remains fairly cool in the hot sun
  • Stain resistant

Cons
  • Slightly rough on the feet (may get rougher over time)
  • Unattractive (to some people)
  • Cannot be applied over existing concrete (at least not easily)