There are, literally, hundreds of different exercises you can do at home or at the gym. This amount of variety is often important as it keeps things fresh and stops you from getting bored and giving up. But, what if you hate complexity? What if you just want to do a few exercises and then get back to your life?
I got you!
There are three exercises that I believe are just about the best you can do in order to get a full-body workout. Of course, this is subjective and you (and many web trolls) may not agree with me, but if you want a full-body workout that you can do in less than 15 minutes and know that just about all of your major muscles are getting whipped into shape, then please read on.
Push-ups

Push-ups are easy to do–and by easy, I mean you don’t need any equipment or a lot of space. You can do them at home or at work–I’ve even done them in a cramped cabin on a cruise ship.
Muscles worked (in order of effort): Chest, shoulders, triceps, abs, obliques, biceps, quads, back.
Too hard? Use your knees instead of toes, or do them at a slight angle against a wall.
Too easy? Put your feet up on a chair or do shoulder taps. Or, the one my own trainer favors, turn a Bosu ball upside down and do plyometric push-ups (I love to hate those!)
How many? Start by doing as many push-ups as you can do without just bobbing your head or hunching your back. Take that number and then multiply by 0.75. You did 15? Your number is 11. Do three sets of 11 (take as much time in between as you need).
Squats with a dumbbell shoulder press

(Also known as Thrusters!)
Grab a couple of dumbells (or a couple of tin cans or bags of sugar) and perform a squat. On the way down, think of yourself sitting on an imaginary chair–or even have your butt touch a real chair briefly. On the way up push the weights over your head.
Muscles worked (in order of effort): Quadriceps, glutes, hips, hamstrings, calves, shoulders, back, triceps, abs, biceps
Too hard? Put down the weights and just raise some imaginary dumbbells. Still too hard? Squat half-way down with one hand holding a chair back for stability.
Too easy? Too easy, huh? Try upping the weight of your dumbbells or do a Bulgarian Split Squat.
How many? See how many you can do in one set without your knees wobbling or your arms starting to struggle (don’t go to absolute failure). Take that number and multiply by 0.75. Do three sets.
Side planks

Side planks are a great way to work your obliques and other stabilizer muscles from head to toe(s).
Muscles worked (in order of effort): Obliques, quads, hips, back, chest, and many muscles you didn’t know you had!
Too hard? Bend your knees and let them touch instead of your toes.
Too easy? Try some reach unders, or place your hand/forearm on an exercise ball.
How long? Start by holding a side plank for as long as you can before you start trembling or your hips drop down. Make a note of that time and try to do three sets with that as your target time. Stop whenever you feel too much discomfort or break the correct form.
Of course, all three of these exercises are just suggestions. Ideally, you should work with a certified personal trainer. The reason? A good trainer will do a range of assessments first to make sure any exercise doesn’t compromise your capabilities, health, joints, etc.