Seven Tips for Making Amazing Homebrew Magic Items
1. Give the Magic Item a Name - "Razor's Edge" or "The Golden Smite" is a lot cooler than "+1 Rapier" and your players will love using its name when they strike down the enemy!! “You will suffer the wrath of the Blade of No Tomorrow!!”
2. Mimic a Feat - A trident with Sentinel abilities makes a cool magic item. Maybe your players have found a pair of Lucky Socks or the Gloves of Shandowart which gives them the Magic Initiate Feat. What about the Slippers of Mobility or a saddle that gives you Mounted Combatant? You can even use feats no one would waste a feat on... like Weapon Master.
3. Mimic a Spell - Spells (even cantrips) are great for Magic Items. Make a Wand of Healing Word with 3 charges or a Ring of Prestidigitation. If it works for a Ring of Three Wishes it can work for any spell. A Bag of Goodberries... Sword of Wrathful Smiting... Hat of Haste. This is a great way to use spells that no one ever uses like Mordenkainen's Sword. You could even have a blade that casts True Strike as a bonus action 3 times per day.
4. Mimic a Character Ability - Character abilities are so much fun and magic items can give your characters even more. Boots of Wildshaping... Gloves of Flurry of Blows... Rage Hammer... Wand of Spell Sculpting. Just be careful not to step on the toes of other characters. If you have a monk in the party, don't pass out those gloves. It will make them feel less special.
5. Curses - Most cursed items are boring. The character tries to get rid of it as soon as possible. Make cursed items awesome so the character is willing to live with the curse. A Vorpal Blade that smells like farts... Flying Broom of Crashing... Holy Avenger of Criticism… Bracers of Strength and Anger. Use minor curses that are an acceptable price to pay for the power of the magic item.
6. Modify Existing Magic Items - You can change things up. Instead of a Frost Brand, you could have a Thunder Brand or Acid Brand. Instead of a Staff of Fire, you could make Gloves of Fire. Bag of Holding becomes Hat of Holding. Cloak of Elvenkind becomes Cloak of the Gnome. A simple change and a cool name and suddenly you have an epic homebrew magic item.
7. Use Items No One Else Uses - All the magic items seem to be cloaks and boots and gloves, but no one ever makes magic socks or shirts or pants. What about a Shirt of Mending or a comfy pair of Undies of Warmth? Pants of Speed would make more sense than boots since your legs are doing all the work when you run. What about Socks of Stealth or Undershirt of Resistance to Piercing?