General synonyms:
* Enthusiasm
* Vigor
* Zest
* Ebullience
* Vivacity
* High spirits
* Joyfulness
* Rapture
* Passion
* Excitement
More specific synonyms:
* For energy and vitality: Forcefulness, Spontaneity, Overflowing energy
* For emotional intensity: Euphoria, Rhapsodic, Ecstasy
* For enthusiasm and excitement: Zeal, Fervor, Ardour
The best synonym for you will depend on the specific situation and the shade of meaning you want to convey.