"My god(s), it's full of stars!" expressing fascination with a plasma grenade/fuel rod gun explosion killing an enemy.
"I no hate humans, he does!" When running away in the presence of friendlies.
"He was almost out of air anyways..." At the death of a fellow grunt.
"More food nipple for me!" At the death of a fellow grunt.
"He owed me money!" At the death of a fellow grunt.
"Oh what's the use..." Death of leader (elite, high ranking grunt, etc...)
"Can't we all just get along?" Running away, death of fellow grunt.