You can tell right away if a dude lifts by his shoulder width. If you're tired of hearing "Oh, you lift weights?" then give this lateral raise modification a try.
Escalating Hold Lateral Raise
Grab a weight that's about 50% of what you can do for 10 reps. Why 50%? You'll see.
Lift the dumbbells so your arms are parallel to the floor. Hold them in this top position for as many seconds as the rep. So on rep 1, you'll hold the top position for 1 second, rep 2, you'll hold for 2 seconds, etc.
Go to 10 reps, which means you'll hold the last rep for 10 seconds, then rest for 1-2 minutes and repeat. Go for 2-3 sets.