General Happiness:
* Joyful
* Cheerful
* Delighted
* Glad
* Pleased
* Content
* Elated
* Euphoric
* Blissful
* Exuberant
* Merry
* Thrilled
* Lighthearted
More Specific Feelings:
* Excited: Full of anticipation and eagerness.
* Grateful: Feeling thankful for something good.
* Satisfied: Feeling content and fulfilled.
* Peaceful: Feeling calm and tranquil.
* Hopeful: Feeling optimistic about the future.
Formal Synonyms:
* Jubilant
* Ecstatic
* Beatific
* Rapturous
Informal Synonyms:
* Tickled pink
* Over the moon
* In seventh heaven
* On cloud nine
* Giddy
The best synonym for "happy" will depend on the specific context and the emotion you want to convey.