C/1

Call Lightning

In-game, this one is an interesting contrast with the better-known Lightning Bolt: worse in some ways (you can really only cast it outside or in a huge room, and it doesn't do as much initial damage) and better in others (higher damage at higher levels, and it can last up to ten minutes, with the caster being able to blast an enemy with lighting on every turn).  But that's just nitpicking. Is this an effective real-world spell? You bet your ass it is. Even if some people survive getting hit by lightning, calling down electrical bolts from the heavens to smite your enemies is classic wizard shit.

Real-World Rating 7 (Effective)

Calm Emotions

The only thing this does that you couldn't do with a handful of valium is work on a crowd. I'm trying to think of a real-world situation in which this wouldn't be just a temporary distraction, and it's hard -- this is your typical RPG debuff, which is contingent on their being buffs in the first place. I suppose it might be fun if just fucking with people is your idea of a good time, though.

Real-World Rating:  5 (Effective But Limited)

Chain Lightning

One of the classic high-level offense spells for a wizard, this is essentially Lightning Bolt Plus Plus: If you're casting this at a high level, you could theoretically cause something like 320 hit points of damage. So it's fine, it's a fucking lightning bazooka, nothing wrong with that. What I want to talk about here is the material components: a bit of fur; an amber, glass, or crystal rod; and three silver pins. Who walks around with all this shit in their pocket? Who is going to able to fumble around with all these annoyingly tiny, breakable, and possibly capable of giving you a nasty booboo items when there's a huge griffon trying to tear your face off? I get that this was supposed to be an example of sympathetic magic, and it makes for good color, but it's also why I've literally never played in a D&D game where anyone paid any attention to the material component requirements.

Real-World Rating: 8 (Very Effective)

Charm Person

One of the all-time classic D&D spells, and a slick way for low-level characters to get past guards and the like. The devil is in the details here: charmed persons regard you as a "friendly acquaintance". Maybe the limits of this were a lot more malleable in medieval times, but now it's going to crash headlong into technology and at-will employment. I know a lot of people who would probably think of me as an actual friend, not just a friendly acquaintance, but they're not going to let me take home a bunch of free shit from their job. Even if I was romantically involved with a bank guard, she wouldn't let me open the vault if I just showed up at her job and asked, because there are video cameras and she doesn't want to get fired. 

There's also the massive downside of the target knowing that you basically mind-controlled them after the spell wears off, meaning you effectively guided someone on a path from Total Stranger to Friendly Acquaintance to Hated Enemy in the space of an hour. Not as great as it is in game terms, but it's probably good for your ego to think everybody likes you.

Real-World Rating: 4 (More Trouble Than It's Worth)

Chill Touch

Actually a lot better than it seems. The undead part is a wash in the real world, and it doesn't inflict a ton of damage (although, again, enough to kill or seriously wound most normal people), but dig this:  You get to make a horrible sickly glowing ghost-skeleton hand appear out of nowhere, grab someone, and hurt them very badly, and they can't shake it off for a whole minute! Creepy. And it's a cantrip, so you could just keep doing it all day!  You would be able to freak out entire rooms full of people.

Real-World Rating: 6 (Pretty Okay)

Chromatic Orb

Not bad offense for a 1st-level spell: 3d8 damage with a successful hit (although that's low odds for a wizard), and it can take on different forms tailored to your enemy's weakness. Still, it's not playing the percentages, and if you take the material component into account, you're spending $50 a pop for something that might just miss completely. A classic just-buy-a-gun spell.

Real-World Rating: 4 (More Trouble Than It's Worth)

Circle of Death

Now we're talking!  Circle of Death!  Circle of Death! CIRCLE of mother-fucking DEATH! But that's how they get you: the metal-as-hell name is just there to sucker you in to blowing 500 gold on a spell that does a maximum of 48 hit points of damage (as opposed to, you know, instant death) to any given target. Not that 48 points is anything to sneeze at, but the distance between what the name implies and what the spell actually does is continental. Lightning Bolt does the exact same amount of damage and you can cast it at 5th level as opposed to 11th for this dud.

Real-World Rating: 6 (Pretty Okay)

Circle of Power

This is a great amazing-in-the-game, useless-in-real life spell. It's basically a mobile anti-magic field, letting you surround your pals with magical energy that protects them from other magic and buffs their saves. But in the real world, remember, you're the only one that can do magic!  And the saving throw buff this spell gives you is only useful against magical spells and effects! So it's...

Real-World Rating: 1 (Worthless)

Clairvoyance*

This is a spell whose major effect -- the ability to see or hear something from up to a mile away without being physically present -- sounds pretty great, but has largely been superseded by technology. Because of the in-game limitation of both distance and a requirement that it be a place you're either already familiar with or is "in an obvious location", it doesn't let you observe anything that's really concealed. Under such restrictions, you're better off just using a small digital spy-cam, which has the advantage of letting you see and hear what's going on, and, if connected to the internet, can work from thousands of miles away.

Real-World Rating: 4 (More Trouble Than It's Worth)

Clone

The rare high-level spell that's even better than it sounds. A perfect clone -- no, not perfect; better than perfect, because you can make your clone a younger version of yourself, guaranteeing yourself immortality for all intents and purposes! Plus, none of this nature/nurture bullshit; it has all your physical traits, memories, personality, and abilities. It doesn't need to be tended to, and will sustain itself indefinitely if undisturbed. And it hasn't (yet) been improved upon by technology! The spell only takes an hour to prep and the clone is out-of-the-box ready in four months, for the low, low price of less than $4,000!  For eternal proof against death! Don't let Elon Musk find out about this one.

Real-World Rating: 10 (Essential)

Cloud of Daggers

It's no Blade Barrier, but again, creating a five-foot-square whirlwind of slashing knives is enough to give most people pause when they're deciding whether or not you are a person they feel like screwing with. I also should mention that if you cast this spell at 3rd level, it does the same amount of damage (and without a saving throw, and for up to a minute!) than Circle of So-Called "Death".

Real-World Rating: 6 (Pretty Okay)

*: This also lets you hear things remotely (clairaudience), but sadly does not give you the option of clairosmia, or smelling things remotely. I can't imagine why.