i used to use one fly spell in combination with a lot of levitate spells. fly on one pc, levitate on the rest who are holding onto a rope, and you have pc's as kites, all flying with the use of one fly spell.
another one i used to do is to reverse the enlarge spell, shrink the whole party down to one foot tall, throw them all in the portable hole, allowing the wizard to teleport up to a dozen or so people with one spell.
i used to use the amulet of the planes to teleport to the positive energy plane to heal up hp's ultrafast
used same item to go to elemental planes, where i could rest up at twice the normal rate (per old manual of planes) and memorize spells faster.
i had party members cast spells at me while holding the staff of the magi so i could recharge it.
timestop with delayed blast fb was a hell of a lot of fun. stick the tiny marble up people's shirts, etc.
my all time favorite use of a magic item though was by a character with a mirror of mental prowess, from first ed dmg.
Mirror of Mental Prowess: This magical mirror resembles an ordinary one.
The possessor, however, knowing the proper commands can cause it to
perform as follows:
1. Read the thoughts of any creature reflected therein, even though
these thoughts are in an unknown language;
2. Scry with it as if it were a crystal ball with clairaudience, but even
being able to view into other planes if the viewer knows of them
sufficiently;
3. It can be used as a portal to visit other places (possibly other planes,
as well, at the DMs option) by first scrying them and then stepping
through to the place pictured - an invisible area remains on the
“other side”, and those using the portal can return if the correct
spot can be found. (Note that creatures being scried can step
through also if the place is found by them!);
4. Once per week it will answer one short question, briefly, regarding
a creature whose image is shown upon its surface.
the player used option 3. he scried out a location just behind where he was standing, then moved only halfway through the mirror, thus proving once and for all that when you tell someone to go f*** themselves, in d&d, it is possible.