Some apps have them. Amethyst & Nostrudel have a wide selection, and you can add custom ones even.

As with many things on Nostr, this depends on the client you are using. Many clients only have one reaction option to "like" a post, while others will allow you multiple options to choose from, and a few will let you create custom reactions. Bear in mind that the farther you get away from something that can be interpreted as "liking" a post, the less likely that clients with only one option will display your reaction at all.