Unfair and deceptive trade practices include any "trademark infringement", such as selling "Rollex" watches that are designed and marked to look like the more expensive "Rolex" brand.
Another common advertising scheme is "bait and switch" where a merchant advertises product or service X, but it is somehow "unavailable" when customers request it, but the customer is offered goods or services Y at a higher price.
Use of the word "free" or "free sample" or "free offer" is also abused by many, where the "Free" aspect means you have to first sign up for a subscription you don't want, or otherwise make promises of future payments for things you don't want. Those obligations are NOT considered "free" and can be illegal if not properly limited by the "fine print" you often see in "disclaimers" (e.g., "void where prohibited, merchant reserves the right to cancel, customer agrees to terms a,b,c, and to return the sample if not satisfied", etc).
One esoteric unfair trade practice is attempting to enforce something that a customer was unaware of or that violates local laws. For example, Massachusetts has laws requiring a certain amount of warranty on any "household products", meaning that anyone purchasing such goods automatically has that warranty (i.e., that it is what it says and that it will actually work as advertised). Some merchants may try to bully a disappointed customer who is returning a defective product by saying things like, "you had to return it within 14 days", or "you didn't buy the extended warranty", both of which are illegal, assuming the product is actually defective as delivered (i.e., it doesn't work the way it says it will).
The racist angle is obvious, where someone advertises things like, "Darkie Toothpaste", which I actually saw in Singapore, using actors in black-face and zoot-suits. The brand is owned by Colgate-Palmolive, which "changed" it to "Darlie" (which in Chinese still means "black person").