Von Restorff Effect
The von Restorff effect (named after Hedwig von Restorff) predicts that when you're presented with multiple things that are the same, the one that is different from the rest is more likely to be remembered. It's also known as the "isolation effect".
An example would be if you're given a shopping list with one item highlighted in a bright color, you'll be more likely to remember the item that was highlighted. Or if you're give a list of words like this:
you would be more likely to remember "car", because it's different from the meanings or category of the rest of the words.