Magic items should be a fun part of your game, but its all too easy to hand out a +1 shield and move on. DMing involves juggling a whole lot of things at once, and its not always convenient to stop and write up some flavor for that shield.
Here's a couple of magic items with character to keep in your back pocket in case the need for one should present itself:
The Seer-Sword of Nahr. This slim-bladed longsword is set into an ornate, white-jewelled pommel and a crossquard depicting a maiden with outstretched arms wrapped in some sort of ropy vines or mists. Faint runes are visible on the blade just above the crossguard, and magical deciphering interprets them as reading "Truth Eternal". The Seer-Sword functions in combat as a +1 longsword. Additionally, once every 33 days it can summon up the spirit of one intelligent being it has been used to kill within the last 333 days, and compel that spirit to answer 3 questions. Unfortunately, since most of the spirits called are none too happy with the weilder of the blade, there is a 1 in 20 chance per question that they give a malicious lie for an answer, designed to harm to the weilder in some way.
Glolmir, the Hammer of Life. This simple-looking warhammer is made of age-darkened iron, marred with dozens of dents and nicks, and bears a single, tiny holy rune on the business end of its head. The pommel is wrapped in sweat-darkened leather straps, and is slightly bent. Glolmir functions as a +1 warhammer, but is +2 against all forms of undead. Once per day, immediately after it has been used to strike down an undead foe, the weilder may tap a nearby friend with the Hammer of Life and grant him healing equal to the amount of damage inflicted upon the slain enemy. Glolmir is a restless weapon, and will disappear after one year, ostensibly placing itself in another dungeon somewhere for the next hero to find.
Aerys Knife. There are at least seven Aerys Knives known to exist. The weapons are made of some very light, porous metal and hilted in cork. They are said to be very ancient; relics of a lost empire. Areys Knives function as a +1 Dagger, but are +3 to hit (not damage) if the combat is taking place in water. If placed carefully into a bowl of water, the Aerys Knife will float, and will always move slowly to point to True North, so these blades can be a valuable aid to explorers lost in the Underworld.