Hunger of Hadar is an disgustingly underrated spell and that's probably because its a Warlock exclusive spell.

100% Find Familiar. Yes, there are far more powerful summoning spells, but the flavor and roleplaying potential cannot be understated. Any wizard that doesn't take Find familiar at some point in their first few levels is seriously missing out. 

Whenever I play a wizard, the first spell I ever cast in the campaign in almost always Find Familiar as a ritual. It's just too good in every way.

Flock of Familiars is awesome. One of the coolest I've heard of is Geas, which is an amazing mind control spell, especially if you're trying to kill the target. 

My favorite is scorching rays. while it has no roleplaying purpose its pure amount of potential firepower is stupendous with three rays each rolling a d10 for damage and the potential for more rays the higher level the spell, it can eviscerate or heavily weaken tough enemies in one blow.

Find familiar. This one 1st level ritual spell can give you the following 6 benefits:

1. the abilities to see through its eyes, and hear what it hears while within 100 ft of you
2. deliver touch spells from up to 100 ft away from your target
3. the benefits of its help action, which gives you advantage on attacks

Suppose you choose an owl for your familiar.

1. 120 ft darkvision
2. Advantage on Perception checks involving vision or hearing
3. Flyby - the ability to avoid provoking an opportunity attack from a target

If I'm playing any class that doesn't have access to a familiar, I strongly consider the Wizard Magic Initiate feat just to get access to this spell.

Heat metal

Turns armor again anyone who thinks they are safe.

Chrono Stasis. I love watching the look on my enemy's face when that 5th level fireball they cast does nothing!

Quote from burningkings >>

My favorite is scorching rays. while it has no roleplaying purpose its pure amount of potential firepower is stupendous with three rays each rolling a d10 for damage and the potential for more rays the higher level the spell, it can eviscerate or heavily weaken tough enemies in one blow.

 It's 2d6, so it's even better. Flaming Sphere also has comparable damage.

My favorite spells are Frostball (( if any day WoTC could implement it )) and Magic Missile.

Thunder Step: being able to do a damaging teleportation spell has led to some pretty hilarious & cinematic moments (made better by the spell’s ability to bring a partner along with you).

Friend trapped behind a locked gate or in a pit of monsters?

Dive after them & teleport them to safety, giving those beasties a final parting gift of thunder damage.

Bigby’s Hand is another great spell for describing quirky ways to hurt your enemies: flick them away like a bug…declare a “thumb war” with the opponent’s skull…have the hand crawl across the floor like a creepy spider, etc…

Animate Objects is another…I either like to make it spooky, like my character is a poltergeist, causing pots & pans or other random objects to shake with supernatural horror…or get creative with some, say, cannonballs or vials of acid.

Ok, I never really got the point of Message. WHY IS IT SO HELPFUL? I've personally never found a use for it.

Quote from ShortFort >>

Ok, I never really got the point of Message. WHY IS IT SO HELPFUL? I've personally never found a use for it.

 Just played a game last night when it was used. We were rescuing some prisoners who were tied up across a large room. Caster used message to communicate with them to gather intel before planning our rescue. Cool thing is you can use the spell on a total stranger, and there's no save to resist it.

Shield
Absorb Elements
Fireball

In that order.