Good luck is an expression that we use to wish someone the best in their future endeavors. There are many ways to say good luck that can be used in different situations. Some synonyms for good luck include all the best, break a leg, best of luck, good fortune, wishing you success, hope everything works out, fingers crossed, and Godspeed. Each of these phrases can be used to convey hope and support for someone's upcoming endeavors. While the use of good luck is a common and accepted phrase, using different expressions can add variety to your vocabulary and convey more sincere wishes.