The downside to this is that Warlocks can only use a very limited number of spells at a time before having to rest to use them again, so knowing which ones you like to use the most are important.
These are my top ten Warlock-class spells and cantrips.
10. Hold Person
The target has to make a Wisdom Saving Throw, or be paralyzed for the duration of the spell.
I figure the squishier classes like Warlocks probably shouldn't be on their own in a situation where using a spell like this should really come up, there should be others around that could more easily and physically take care of things like that.
Still, it can be useful in certain situations, like if maybe you're on your own and want to subdue someone without getting too close or accidentally killing them.
9. Spider Climb
This spell lets a creature crawl on walls and ceilings and across other surfaces, and even lets it leave its hands free.
While I like it, I find its only really useful until you're able to get the Fly spell.
8. Remove Curse
As the name implies, it allows you to remove a curse from an object or creature.
It could be useful depending on the kind of game you're playing, I myself just don't end up running across a lot of cursed objects or people, so I don't find myself taking it much.
7. Poison Spray
The name's a little deceptive; the spell doesn't really spray poison, but creates a cloud of gas that flies towards the target. It's not super-versatile like some of the other spells, but I like having a non-Eldritch Blast cantrip just in case that doesn't work against my particular opponent.
You can probably come up with a lot of different uses for this spell. It lasts up to an hour, and can be cast on multiple creatures at higher levels.
I like this spell, I just don't feel like I get to use it a lot.
5. Comprehend Languages
Quite versatile, it allows you to understand spoken languages and read written ones, even if you don't actually know the language. It doesn't decode secret messages or things like that, it has to be an actual language.
It's nice to have. Using it requires a spell slot, but it's quite helpful if your party's known languages aren't very diverse.
4. Hellish Rebuke
This spell lets you use a reaction to taking damage to damage the creature that damaged you. It has a range of 60 feet, but unless you're facing something with lots of long-ranged attacks, that should be more than enough to hit whatever just damaged you.
As a magic user, you might not have as much health as some of the tougher classes. If something gets close enough to damage you, it's nice having this spell to damage it and either take it out or soften it up enough for whoever attacks it next to prevent you from taking more damage than necessary.
There's very little I find better than flight, even if it's only temporary. It lasts for ten minutes, gives you a flight speed of 60 feet, and lets you cast it on multiple creatures at once at higher levels.
It would be higher, but you can't get it right away, unlike cantrips, and using it still takes some of your limited spell slots, so you can't just use it repeatedly. Still, it can be game-breaking when used correctly.
2. Mage Hand
Endlessly useful for all kinds of tasks, this cantrip instantly produces a magically floating hand with a range of 30 feet. It can only lift up to ten pounds and disappears if it moves outside its range, but it's excellent for pulling up small objects, potentially-trapped chests from farther away than normal, and other tasks that you'd prefer to stay away from while completing.
1. Eldritch Blast
A very important spell for Warlocks, this can become a very powerful spell. At first, it only shoots a single beam. At higher levels, however, it can shoot multiple beams, each separate one doing a d10 of damage. These beams can be directed at the same or multiple targets.
As a Warlock, once you reach level 2, you can start taking invocations that can change the way your spells or abilities work, or give you new ones entirely. Several of these specifically power up Eldritch Blast. You could potentially have an Eldritch Blast with a reach of 300 feet, with the ability to push back those hit, and your character's Charisma modifier added to the damage.
This can potentially become an extremely powerful spell with many different uses in combat. I think this versatility and power is why it's my favorite.