little, slight, small, soft
low
non-committal
He gave a non-committal grunt in reply.

loud
angry, annoyed, frustrated, etc.

give, let out
hear

with a grunt
He lifted the heavy box with a grunt.

grunt of
a grunt of pain

loudly
softly
angrily
merely, only
He merely grunted at her and nodded his head.

at
His father grunted at him as he left the room.

in
She asked him a question and he grunted in reply.
He grunted in pain.

with
She stirred the soup, grunting with satisfaction.

grunt and groan
Grunting and groaning, they heaved the wardrobe up the stairs.

Grunt is used with these nouns as the subject:
pig

Grunt is used with these nouns as the object:
acknowledgement, reply