Plans to go bungee-jumping might be fun if your friend group is full of risk-takers, but it won't be an enjoyable activity if many of you are faint of heart, or lacking in courage.
You'll most often see this expression in the phrase not for the faint of heart, used to describe things that take a lot of courage or grit: "Nursing is a rewarding job, but it's not for the faint of heart." "Climbing those cliffs is not for the faint of heart." It also has an adjective version: faint-hearted. This use of faint comes from an older meaning of the word, "feeble" or "cowardly."