General synonyms:
* Throaty
* Raspy
* Hoarse
* Rough
* Harsh
* Deep
* Gravelly
* Thick
* Heavy
Synonyms emphasizing the origin of the sound:
* Pharyngeal
* Laryngeal
* Palatal
Synonyms emphasizing the effect of the sound:
* Unpleasant
* Unmusical
* Unmelodious
* Coarse
* Unrefined
The best synonym to use will depend on the specific situation. For example, "throaty" might be a good choice if you're describing a singer's voice, while "rough" might be better for describing a cough.
It's also worth noting that "guttural" can also be used to describe something that is related to the throat, such as a guttural reflex. In this case, you might use synonyms like "pharyngeal" or "laryngeal".