Pet stains and cola stains.
We like a product called Blue Magic. We purchase from local AutoZone. It really works well.
Krud Kutter original took it out of car carpet.
First, I would use Spot Shot - the absolutely BEST carpet stain cleaner (for smaller stains). For larger stains, I would mix an oxygenated cleaner like OxyClean or Awesome Orange with warm water and apply liberally with an old towel.. Scrub well and rinse with clean water. Next, you can replace the commercial rug shampoo with the same oxygenated cleaner mixed with water and use the shampooer to complete the cleaning.