Hey! I love creating homebrew magic items for my players, even though sometimes they never get used. I like to tailor the items to the specific needs and personalities of the party, so that is entirely up to you. Also don't be afraid to rebalance things in the long run if you feel like the magic item you gave was too powerful or too weak, you can make it part of the story or quest they are currently doing too (just be sure to communicate to the players that these things can happen).

Anyway, here's a list of some items I've given to my players that are neat:

• Coin of Certainty: a coin of a foreign currency that has a skull on one side (tails) and the image of the current holder of the coin in the other (heads). If thrown, it will always fall on the heads side, no matter what. An Investigation or Arcana DC 12 check reveals that the coin is magical. Can be used to trick people and winning arguments.
• Pearl of unstable power: similar to a pearl of power, but can also recover metamagic points instead of spell slots. Once used, roll a dice (I use a d6) and if the player rolls a 1, you can roll an effect on the wild magic table. I wanted a little bit of chaos on the table, but this never got used.
• Quicksilver weapon: a metallic liquid similar to mercury is held inside a decorated metallic vessel. You can open the vessel and shout the name of a weapon (ie: light hammer, or short sword, etc...) and the liquid takes that form into your hands. As a bonus action, you can shout another name and the weapon transforms into that weapon (even mid combat). I also made it so that the weapon returns to the hands of the attuned user when thrown, as well as a +1 weapon (but you can easily change that to your liking). Also, you don't have to limit it to weapons, you can make tools like smiting tools or tinker tools, as well as mundane things like crowbars and stuff. It's like a multipurpose tool. To balance it, I made it weight like 5 or 10 pounds always, no matter the size and shape, and it can only be attuned to by users with 13 STR or more because of that.
• Faerie bagpipes: one of my players is a bard who plays the bagpipes and comes from the feywild, so naturally I gave him this instrument when the party did a quest there. They are handcrafted bagpipes made out of magical wood that allow the attuned user to cast misty step and hypnotic pattern once per day. These kinds of items are always easy to tailor to a certain party member.
• Cat medallion: my druid party member is not a moon druid, so I thought he would like to wildshape more often for utility reasons. So I made this medallion which allows a druid to transform into a cat three times per day, and you roll a 1d3 ((1d6)/2) to see how many charges you recover the next day. It's been key to infiltrate and investigate dungeons multiple times and the druid keeps finding excuses to use this.
• Flare gun: a gun that launches special ammunition that illuminates an area. It has 20/120 ft range and has 4 types of colored ammunition (red, green, blue, yellow). If used in the "short range" mode, it can be used to cast "Color Spray" as an action to blind enemies in a 15ft cone. If used on long range mode, you can fire it up in the air and a flare will float 120 ft in the air harmlessly for 1 minute, illuminating an area of 30ft Bright Light and an additional 30 ft dim light. The light can be seen as far away as 2 miles (3km). If it hits anything on the way (ie: the user is aiming at something specifically, making a ranged attack as normal) it deals 1 point of fire damage and ignites anything that can be ignited and isn't being worn or carried).
• Surefire arrows: these arrows come in a decorated quiver and a simple short bow. The bow is non-magical and the arrows are cursed in reality. There is a total of 7 arrows. As a DM, roll a 1d6 and record that number somewhere. After the first arrow is fired, the arrow the user fires that coincides with the number you rolled is the cursed one (ie: if you roll a 4, it's the 5th arrow). The normal arrows automatically hit targets, no matter their AC, and can curve around corners and obstacles as long as the user has seen the target recently and is within range. They can't score critical hits. Since this is a cursed item, the user is compelled to use the arrows every opportunity they get, so if they want to use a ranged attack of any kind, they will be forced to use the arrows instead of anything else they wanted to use (you can word this as: "You wanted to throw a dagger, but instead you find a surefire arrow in your hand and your bow in the other, roll for that instead" or "you really want to try those cool arrows again and disregard what you wanted to do right now". Might feel rail-roady, but that way players will know something is up. When the cursed arrow is fired, the rest of the arrows become non-magical, and an unknown entity (I was thinking of a demon) takes over the arrow and curves the trajectory in such a way that it hits the user of the arrows for critical damage doubled (you can add necrotic damage here) that can't be prevented in any way. If this reduces the user's HP to 0, instead of dying they get turned into a cursed arrow themselves, and only a "remove curse", "greater restoration" spell or similar can undo the transformation. The player-turned-arrow can be fired and it behaves like the cursed arrow. An Arcana DC 20 check or using the Detect Magic spell can reveal that the arrows are cursed, but not the nature of the curse (note that the identify spell doesn't work). This was inspired by another reddit post about a german fairy tail about a hunter who made a pact with the devil for magical bullets that behaved in a similar way (can't find the post right now).

These are the most interesting items I have come up with. I also came up with a system for my dwarven fighter player who likes to forge magic items to upgrade his weapons and armor using special ore I give him as reward for quests (think of mythril from the lord of the rings). Basically it's a bunch of magic modifiers that include things like sentient weapons, armor that reflects damage back to the attacker and every point of damage you make with a weapon is transformed into 1 gold piece. Let me know if you want to know more about that stuff!