Hell's bells is a slang expression used to express shock, surprise, or frustration. It is often used to convey intense emotions. However, there are many synonyms for this expression which can be used in different settings. Some of the popular synonyms for Hell's bells are 'Holy cow', 'Good gracious', 'Oh my goodness' and 'Gosh darn it'. These expressions also convey surprise or disbelief, but in a less aggressive manner. Other synonyms might even be comical such as 'Gee whiz' or 'Jiminy Cricket'. Using these alternatives can be helpful in situations where the use of foul language or aggressive tones might be considered inappropriate.