What if potions and tonics had negative side effects? Potions of increased strength cause violent tempers, or damage joints. What if potions of dexterity caused tremors, or palsy?
What if they were addictive, and had withdrawal symptoms?
Could someone make a bad batch? No one use the brown strength potion!
A simple flag, faded by time and sun, tattered and worn by untold years flying from the pole of a bannerman, passing hands from officer to officer, from one generation to another. It is a humble symbol of great importance, and greater inspiration to those who see it. Soldiers become heros filled with espirit de corps, enemies loose their nerve and fire. It is not an enchanted item, but a powerful item still...
The PCs traveling along the road/path/trail begin to hear a low droning sound. As they approach they find their path obstructed by hundred of thousands of droning insects. Locusts swarm though the air, feasting on the grass and plants. Passage will be slowed, but the insects pose no threat to the party, aside from being crunchy and disgusting underfoot, climbing into pouches and eating exposed food goods.
Expansion from the Horse Brass item: Specific Armor charms.
Cooling Touch Charm: protects horse against extreme heat, and fire, magical and mundane
Jove's Favor: tin charm shaped by a lightning bolt that protects a horse primarily from natural lightning, but also potentially from lightning based attacks. In real life, lightning kills quite a few horses and cattle a year.
Hermes' Blessing: gold charm that grants the horse magic resistance, and perhaps immunity to cantrip level magics.
Vulcan's Steed: This large iron charm in epic fashion renders the steed invulnerable to iron weapons. Such things clatter off of the animal's hide like twigs.
These magical boots empower the wearer with several abilities at once. Wondrous leaping, water-walking, and even flying! Yet the boots possess an insidious curse upon them as well. A deep and almost unfathomable (by others) feeling of listlessness, boredom, and even apathy affects the boots' wearer at all times whenever they are donned. Magic will not dispel the effects.
And so while the wearer of the boots can perform great feats of action during combat or at other opportune times and key moments, they'll never really want to do so, complaining "Meh, what's the point of it all anyway?" or "I would fly up and save us all guys, but sigh, maybe uhm, soonish, mkay? Bit bored by this whole burning tower at the moment."
Naturally the boots wearer's fellow PCs will grow quickly frustrated with this arrangement. There have been numerous occasions when one angry PC literally tears off the boots from his companion's feet in anger, and dons them in turn, only to immediately suffer from the same effects.
The solution lies in constantly "motivating" the boots' wearer with successful rolls, involving threats, flattery, fiery speeches, or even bribery.