I'll try to list things that aren't in the typical internet echo chamber. Bring on the controversy. These are just my opinions.

50% of the shelf space at the grocery store is just different forms of corn syrup, sometimes with some trans fat mixed in, generationally twisting our idea of what food is in a race to the cheapest, most addictive product.

The only way it's profitable for someone to knock on your door to sell ANYTHING is if they are obscenely inflating the price (think 100-600% markup)

Most supplements, especially expensive ones with TV ads

Dr Scholl's and the goodfeet store

Genuine leather is just about the opposite of what you'd think

Bamboo fabric which is pretty much just a different way to say rayon but is pitched as a revolutionary and environmentally friendly cloth

Most bladeless fans just hide fan blades in the base

Many cleaning products don't do better than diluted soap and water (even for sanitizing) especially the ones with TV ads

Financial planners who are actually financial product salespeople

Most single-purpose kitchen gadgets, especially as-seen-on-TV

The realtors racket: I just paid $30k for an internet posting and mediocre advice

Many personal hygiene products are just repackaging the same two or three active ingredients by the same one or two megacorporations

Essential oils (even ignoring mystical claims) big names charge an order of magnitude higher than they should