Spell-Storing Items Are Insane

The Artificer is a half-caster, like the Paladin and the Ranger. You'll never get more than 5th level spells with it, and you'll have to rely on other class features (like the very nice Artificer Infusions) to keep up with pure casters.

Looking through those features, though, one of them stands out as really, really good: Spell Storing Item.

Once you hit level 11, when you finish a long rest, you can touch an item and store a spell of 1st or 2nd level in it - it can be any artificer spell of those levels; you don't need to have it prepared. The spell needs to have a cast time of 1 action, though, so no Shield.

Anyway, anyone can use this item to reproduce the spell, using your spellcasting stats (your spell attack bonus and your save dc, and if it's cure wounds, it uses your Int modifier to determine the bonus to the heal.)

What's crazy about this is that you get to use it a number of times equal to twice your Intelligence modifier - and all you need to do to recharge it is rest.

What this does, effectively, is give you 10 extra 1st or 2nd level spell slots. Admittedly, you have to pick the one spell you'll be using for all 10 of those slots, but that's still 10 more spells to cast than you would otherwise have - and you can even hand it off to others (for instance, you can give a Cure Wounds canister to your monk, who can then zip around healing folks if they go down.)

If you're an artillerist, you get Shatter as one of your Artificer spells, which is 2nd level (it's a 10-ft radius sphere within 60ft that does 3d8 thunder damage, with a Con save to reduce that by half.) While at level 11 3d8 might not be a ton of damage (your Firebolt by that point will be hitting for 3d10+1d8 if you use your Arcane Firearm) but given that it's an area-effect spell, the damage gets multiplied by how many targets you can hit - and if you have a swarm of enemies, that can get really high.

Invisibility is another option - with ten charges, you (or an ally) can drop out of invisibility without too much fear.

The really excellent thing about this is that you can also spread concentration around. Let's say you want to be concentrating on some other spell, but also want to maintain, say, Enlarge/Reduce on your Monk or Fighter. Just let someone who doesn't need to concentrate on one of their own effects do it for you.

Going back to invisibility, you can simply have each player concentrate on their own invisibility spell so the whole group is much better at sneaking.

Like basically all Artificer features, this is also one that I really think you can get creative with in terms of flavor. I like the idea of making metal canisters for various spells, or rigging up some kind of wrist-mounted squirt-nozzle to shoot grease at an area. Maybe your alchemist makes Enhance Ability into a bottle from which you drink to cast it on yourself.

As a half-caster, you miss out on 6th-9th-level spells, but while those are unquestionably more powerful individually than a couple of 2nd (or 1st) level spells, the fact is that the actual, raw spellcasting ability of the Artificer is increased by 67% from this feature (and at the level you get it, it's doubled!)

The Artificer is really a great Swiss Army Knife class. If you are able to figure out things you might need ahead of time, this feature could be incredibly powerful.