keeper
n. countablen. someone or something worth keeping because they are very good or useful. You often use this to describe a person who would make a great long-term partner or a friend you can trust.
n. a person or object regarded as having lasting value or being worth retaining. Informal in register; frequently used in the context of romantic relationships or personal possessions.
He is kind and funny; he is definitely a keeper.
After testing several different models, I realized this old camera is a keeper because it takes the best photos.
While many modern gadgets are designed for quick replacement, this durable leather bag is a keeper that will likely last for decades.
From Middle English kepere. By surface analysis, keep + -er.
In sports contexts, it is a common clipping of 'goalkeeper'.