THE EYES HAVE IT
The observer! The onlooker! The bulbous, protrusion-laden, floating cyclops head known only as... the beholder!
Everyone's favorite eyewitness has been floating around the D&D table since Greyhawk in 1975. Appearances aside, the beholder's coolest feature has to be its numerous eye rays. I've decided to list them and rank them, completely arbitrarily. I'm clearly not a professional, so don't @ me if you disagree. Let's take a look, shall we?
Charm Ray 
A DC 16 Wisdom saving throw isn't impossible, but the fact that it lasts an HOUR and you can't attempt a saving throw again means the stakes are pretty high on this one. We're lucky the rays have to be rolled at random, otherwise a patient enough beholder might manage to charm the entire group, turning the combat into a tea party. Actually, that's kinda sweet. I give this ray 8/10.
Paralyzing Ray 
With a 1 minute duration and repeat saving throws, this ray appears tame enough. Now imagine you've failed that saving throw, and the paralyzing ray was the first of three headed your way, putting you at disadvantage for whatever gruesome mess the beholder sends over next. Yeesh. No thank you. 3/10.
Fear Ray 
Cool name, but as someone who plays halflings with regularity, I can't help but scoff at this one. Besides, who cares if you can't move toward the enemy? It's ugly as heck, I didn't want to be next to it anyway. 2/10.
Slowing Ray 
Remember the scene from Ace Ventura: Pet Detective where Ace visits the mental hospital in a tutu? Don't forget to give your players inspiration if they use a slo-mo voice when this one hits them. More fun than fearsome, I give it 5/10.
Enervation Ray 
Ener-what? One sec, need to Google... "being drained of energy or vitality"
OH. PALPATINE RAY. AWESOME. 10/10.
Telekinetic Ray 
Definitely cool in combat, being able to grab an enemy and just hold them 30 feet in the air at least means they'll fall even if they save. Outside of combat, can not get over the image of a beholder using its telekinetic ray to do small, day-to-day tasks like making breakfast or decorating its lair. Utility alone makes this ray a 10/10.
Sleep Ray 
The combat wears on; the party is bloodied. A dozen minion corpses lie scattered across the floor of the beholder's massive, cavernous lair. The aberration descends slowly from the ceiling, its main eye wide, awful maw pulled into a grin, ready to deal a deadly blow. Slowly, the bard begins to hum an inspiring tune, the fighter spits blood and slowly lifts his great sword, the wizard's frantic murmuring reverberates off the cavern walls... and the paladin passes right the eff out. This ray gets a 8/10 for comic opportunity.
Petrification Ray 
Oh yeah, that's what I'm talking about. That's the good stuff, the OG, the archetype. The reason we're here in the first place. Good old-fashioned Gorgon powers. It takes two failed saves to make the transition complete, but boy howdy are you in trouble if it works. Probably a good idea to only get into combat with a beholder if there's a cleric in your party. Unless you had "become a sculpture" on your bucket list. 10/10 classic ray.
Disintegration Ray 
If the enervation ray is the Palpatine ray, clearly this one can be dubbed a Boba ray. You'd better pray you have enough HP stored away to take this hit, otherwise there are no take backs, no do-overs, do not pass Go, do not collect $200. Dead. Gonezo. Goodbye. Obviously, a 10/10 ray.
Death Ray ️️
I mean, this is just disintegration ray with more damage and less dust. I give it a 2/10 for lack of creativity.
Anyway, thanks for coming to my Ted Talk.