For some it's a choice, for others it's a medical necessity to avoid various foods and ingredients. Here is a great list of alternative foods for those that need to avoid beef, dairy, egg, and gluten.

Beef Substitutions (vegetarian choices*)
Chicken
Jackfruit*
Tofu*
Turkey
Dairy Substitutions
Butter:
Country Crock Plant Butter
Earth Balance
Miyoko's
Milk:
Almond Milk (not all brands are free from cross contact)
Cashew Milk (not all brands are free from cross contact)
Coconut Milk (not all brands are free from cross contact)
Flax Milk
Hemp Milk (not all brands are free from cross contact)
Macadamia Milk (not all brands are free from cross contact)
Rice Milk (not all brands are free from cross contact)
Soy Milk (not all brands are free from cross contact)
Shredded cheese:
Daiya
Follow Your Heart
Violife
Egg Substitutions
Applesauce
Banana
Chia Seeds
Flaxseed Egg
Just Egg (mung beans)
Oil*To learn more about how much for substitutions,
head over to my TIPS ON BAKING PAGE.
Gluten Free Substitutions(do your research on which type is best suited for your needs)
Brands of All-Purpose Flours:
King Arthur
XO Baking Company (also rice free)
Types of Flours:
Almond Flour
Buckwheat Flour
Casava Flour
Chickpea Flour
Coconut Flour (not cup for cup)
Garbanzo Bean Flour
Oat Flour (must be certified gluten free and use purity protocol oats)
Rice Flour*
Tapioca Flour
Teff Flour
Tigernut Flour Read more HERE on the Ultimate Guide To Gluten Free Flours!
*Rice is high in arsenic, it should be consumed in moderation.