The standing dumbbell shoulder press is a classic deltoid-builder (especially the front deltoids) that’s ubiquitous in gyms around the world. Performing the move standing up as opposed to seated allows for more weight to be used.
Dumbbells prevent one shoulder from compensating for weakness in the other
The more natural range of motion vs. the barbell version lowers injury risk
Stronger shoulders help with a multitude of other lifts, as well as sports