This is a gross simplification of the law. There isn't some "gotcha" like some schoolyard disagreement. "I gotcha! You said it! Derik heard it you gotta do it now! Do it Do it! Do it!"

Yes, you can enforce a verbal contract. You'll need to show what exactly you agreed to which is going to be vague due to the nature of a verbal contract. You'll need to show an offer and acceptance, consideration, intention to create legal relations, legal capacity, and certainty. So no, you can't offer to buy your buddy's car for $1 when you're at the bar grabbing a beer and have them say, "haha, deal" and expect to get their car.