I'm fond of magic items.
I like their histories and their powers.
They make them one of the best awards characters can have, and, at the same time, one of the most satisfying things to create by a DM (well, at least for me).
Let's see some important things you need when creating a magic item.
Give a past to your magic item.
Does it have a name? Why? Who did craft it? Why? How? Who previously did own and use it?
Answer to these simple questions and you'll have new ideas for new sub-plots of your campaign or to better develop your homebrew world.
Example: Heartstone is a sword that has been for centuries an asset of the Earls of Stonewall. Many times they did use it on battlefield, defending their Earldom against enemies and mosters. The last Earl lost his title and the Earldom and joined a mercenary company, bringing the sword with him. After his death the sword changed owner often, from sellswords to common bandits.
Beyond "normal powers", give it also something the character isn't immediately aware, but it shows itself only under particular situations.
Heartstone is a +2 sword and anyone wielding it can use it that way. Inside Earldom's borders or if you are a direct member of House Stonewall, you have 3 superiority dice (1d8) for the Parry Manoveur of the Battlemaster archetype. You regain spent dice after every long rest.
With every power come great responsabilities and big troubles.
Remind it to your players, devising drawbacks for your magic items.
You haven't to give curses to any items but you can rule that it works oddly in some areas or under some conditions or that it affects lightly the character's behavior.
Heartstone's wielder must roll a ST CHA DC 11 check. DM makes secretly the roll and keep record of the failed ones. After 5 failed rolls the PC feels pressed to go to Stonewall and after 10 he starts to believe he's the rightful heir of House Stonewall and wants "to free" the Earldom by invaders.
Describe your item. How is it made? Of what materials? Has it any words or symbols carved?
Heartstone has a little Silver wolf on the hilt, symbol of House Stonewall, and its blade is black.
Create some powers which can be activated only by some particular words or phrases.
Use that chances for further adventures, giving new reasons to your players to investigate your worlds.
To activate Heartstone's Parry power you must know the keyword, which is hidden in the crypts beneath the old and ruined Stonewall Tower. It's now a den for a orc tribe.
A simple magic item with those features will grant hours of fun to your players.
It's a goal of your DMing.