Difficult Magic Items

Magic stuff in dnd relatively easy to use and operate. Even limiting a Identify spell to one property per level  or spell it is still easy. RuneQuest items often require a spiritual fight with the item to attune it. Gamma world and that Gygax space wreck module has the artifact table. 

So here are some things to make life tougher for more complex items

d10 Magic Item Problems
1 Requires meditation or long ritual to attune item before use
2 Research in libraries and with sages and bards
3 Experimental magical tests to find what item requires to awaken
4 Sacrifice of goods rare or expensive to activate
5 Ordeal where user must suffer torturous near death continually in pain
6 Alignment required, or possibly a test of alignment commitment
7 Racist item requires a set species to use or only used vs a certain species
8 Religious preference to a committed tithing member of cult
9 Item has limited uses or only usable at certain times
10 Intelligent and mostly unhelpful or annoying or demanding

Sacrifice time and possibly cash to learn to use object or attune to it.
Items require a day for basic items or a week for complex items to attune them. This at least can stop a item being used in current adventure. Possibly a skill might speed this up more.

Research - spend time in library to study device operation.

Experiment - take precautions and train to use the item.

Meditation - hold object in a self induced trance to form a emphatic link.

Ritual - requiring props, a location, dancers, costumes and reading a text or chanting.

Sacrifice - requires material goods ceremonial destroyed, evil objects like blood or a life, material
might be rare or believed extinct in ancient times. Sacrifice certain monsters to unlock power ups.

Ordeal - will only bond to person who is tortured or suffering or even death and return required to use item power. Might be part of ritual or trance too.

Intelligent Items might require a saving throw or a CHA roll to dominate or befriend them. This might take a period of time. Attribute rolls as a additional requirement for other items possible too. Or tests of your attributes to prove you are worthy. A sword might only serve someone strong or might prefer them to demonstrate health or agility.

Alignment preferences mean someone will be less likely to misuse that relic or have it turned on the maker.

Racist preferences are a must for inter race war settings. Might explain why monsters leave weapons in treasure piles instead of using them. Possibly you could make a glove out of species hand to trick item.

Finding goblin and orc weapons is dangerous, some change users alignment or drain a levee from the unworthy as a price.

Intelligent items should be more common the greater the item. The lower ones are empathic and not very bright. Smarter ones or ones with souls of dead or being in them can be difficult to work with and withhold power if the dont agree with your actions. A +5 dagger that only works if used to ambush or murder by surprise because it has a evil assassin soul inside.

Religious preference is pretty tough requirement but some characters might be willing to worship a new god to use a powerful item. Most gods don't mind you praising their siblings or kin or pantheon. You just try and praise them, make some sacrifices or visit a temple occasionally with a possible new convert.

Item has limited uses or limited to being used in certain season or day or night or when stars are right

Limit how many items you can bind perhaps with a stat or equal to level.

Magic item makers in my world love putting conditions on items. Alignment or race are common requirements. Sad that goblin mace +3 CE is unusable for a neutral human but maybe you can trick it by pouring goblin blood on it every fight). Might be a good way to coerce players into a more extreme alignment than oh so uncaring selfish neutral.

I might make some magic item cards up for special items found beyond the common stuff. Little character sheets or little zines. Possibly make up some hoard generation tables for different peoples. Barbarian, hill folk, goat men, viking, necromancer. etc. Could include some common magic stuff as i have described with a few special ones.