Dump Them All

There are many ways for a romance arc to end. Sometimes there is a normal hookup, one or both die, or the situation is left ambiguous. There are more options involved when in a love triangle, however. For example, apart from the previous scenarios the character may pick several of their options at once. But sometimes they go the opposite direction and reject all of their options. As such, they Dump Them All.

Contrast Marry Them All and No Romantic Resolution.

Beware, this is an ending trope. Unmarked spoilers ahead.

Examples:

Anime and Manga

The Scheris/Mimori/Ryuhou love triangle in S-Cry-ed ends with Scheris dead and Ryuhou rejecting Mimori despite his implied attraction to her because he feels it wouldn't be right. Although he displayed no attraction to Scheris either, she died for him.

Film

By the end of The Green Hornet, Lenore is only interested in a working relationship with Britt and Kato, though both of them have been pursuing her romantically.
The heroine of Catch That Kid rejects both of her male friends as love interests at the end of the movie.

Live Action TV

In the backwards episode of Seinfeld, one woman chooses this solution.
In the original Beverly Hills 90210, this is how Kelly resolves the Dylan/Brandon love triangle. "I choose me!"
In Full House, DJ takes this option when asked to choose between Nelson and Viper, reasoning that if she were really into either of them then she wouldn't have any trouble deciding who to be with.
In the finale to the first season of Community, Jeff is torn between Brita and Prof. Slater. He essentially chooses this option when he decides to leave as opposed to making any decisions. He briefly dates to Brita in the premiere of season two but only so that people would stop hounding him about it. The "relationship" is over quickly, though.
The finale of True Blood season four is a good example: Sookie turns down all three of her love interests. In the case of Bill and Eric, it's a classic "I'm not picking either of you" ending to a Love Triangle. Alcide gets a gentler "sorry, but I don't feel that way about you" rejection.

Theater

George Bernard Shaw's play Mrs. Warren's Profession ends with Vivie turning down proposals from both her suitors. She chooses to devote her life to her career rather than marry.