Arrow necklace
If you’ve paid any attention at all to the characters and their relationships in the Marvel movies, then you’ll be aware of the strong connection between Natasha Romanoff’s Black Widow and Clint Barton’s Hawkeye. You get little hints about the nature of their relationship as the series progresses.
There’s also a lot of fan fiction written by people who wish they were a couple, even though Clint is perfectly happy with his little civilian family. However, their bond is strong, and this is referenced by Natasha’s necklace worn through the films with its pendant in the shape of an arrow.