I've been spending a lot of time in hardware stores recently. The whole place looks like a rich emperor's tomb, full of treasure, strange items, and curious symbols. If your PCs find loot, consider turning to the nearest hardware store flyer instead of the usual appendix. After all, you were going to bin it anyway...
Theme music. Each item below is worth 50gp, give or take.
1. The Immortal Tree
Made of something like hair or resin. 10' high, glows like the northern lights but without any heat or sound. Will never age or fade, but produces no seeds.
2. The Anti-Elemental Ray
A bulbous mechanical end piece attached to a long, cannon-like snout. There's a bright red trigger. If pulled, it makes a high-pitched noise and air whips around near the end of the cannon's snout. It can pick up small objects (they vanish), but it utterly terrifies air, water, and fire elementals. They will flee from the ray if possible. Range is only 2', but the snout is 5' long.
3. Mindless Turtle
Some sort of automaton the size of a plate. It slides around, bumping into things and whistling. It would make a fine distraction but a lousy pet. It will sense and avoid pressure plates and pit traps, but it takes 10 minutes per 10'x10' square, and it sometimes misses squares.
4. Fantastic Cooking Pots
Lighter, cleaner, and sturdier than anything you've seen. They have a coating that makes them very easy to clean. The pots are worth twice their market value if a demonstration is performed.
5. Box of Jewelry
An entire array of dozens of little hexagonal L-shaped pieces of silver metal. They must have been used as jewelry or ritual items, or possible musical instruments. There are dull black ones in different cases, but the silver ones are the most pleasant to look at.
6. Dense Oil
A jug of pale yellow oil. It won't burn or smoke if heated. It's very slippery. The oil isn't horrifically, instantly poisonous, but it clearly doesn't taste like cooking oil. There's enough oil in one bright yellow jug to coat 20 10x10' squares completely.
7. Dark Mirror
A large horizontal mirror, wider than it is tall. It reflects light dimly. There are small symbols on the side, but they don't seem to do anything. It might be a portal to another dimension. The mirror is very large and much finer than hammered copper or polished steel mirrors.
8. Set of Daggers
Ten small daggers, five large daggers of varying sizes, and a wavy ritual dagger. All are sharp and bright. The daggers deal 1d6 damage but never require sharpening. They are also clearly exotic and will impress anyone interested in arms and armour.
9. Boxed Lightning
A palm-sized black box with a white lightning bolt on one side. Two thin ropes made of some smooth material come from one side, ending in metal prongs. Anyone touching or touched by both prongs takes 1d6 lightning damage. The box can be built into a weapon or a trap easily. It can discharge 4 times per day, and automatically recharges if left unused for 12 hours.
10. Tube of Jeweled Balls
A clear glass tube the size of a small barrel, full of red, white, and gold balls the size of plums. They are made of some very light metal. They are hollow, and could contain a potion or a drink, but they are now empty. The items are beautiful. There are 30 balls in each tube.
A blue handle with a trigger, connected to a 5" wide serrated tub or bowl. If the trigger is pressed, the serrated tub spins. It can drill a hole through stone, steel, or wood with equal ease, but only 1' deep at a time.
12. Tiny Poison Vials
There doesn't seem to be any use for these things. They are tiny metal tubes, 20 to a packet, full of bitter and mildly corrosive liquid. The poison is not deadly, but it does cause 1 damage and require anyone ingesting it to Save vs. Constitution or vomit. Alchemists will pay double market rates for these vials.
13. 50' of Hollow Rope
This bright green rope is hard to tie, but it is very strong, and it is hollow. You could use it as a siphon, or pass a smaller line down an existing rope. It can be cut with any weapon, but it takes 2 rounds of strenuous activity.
14. Confusing Goggles
These goggles are clearly meant to be worn, but they are uncomfortable and seem to shift perspective. Any illusions viewed through the goggles appear flat and unconvincing, like paper cutouts. Every hours, someone continuously wearing the goggles must Save or take 1 temporary Wisdom damage (in the form of a headache).
15. Mysterious Salt
A huge bag of blue salt. It tingles and tastes exotic. Anyone who eats the salt for a month must Save vs Constitution or permanently lose 2 HP.
16. False Wood
Large planks, 8' long and 4" wide, of grey wood... except it's not wood. It only looks like it. The core is some sort of dust. The planks would make a very exotic floor or wall covering for a palace. They can also be used to frighten dryads or other plant-based creatures. They must make a Morale check when the plank is first presented, and cannot approach within 20' if the check is failed.
17. Heated Coat
A thick, very warm coat with a symbol above the heart. The coat heats itself to a slightly-warmer-than-comfortable temperature, but it does so in any weather. Anyone wearing the coat gains a +4 bonus to any checks against frostbite or cold, and may automatically pass some tests.
18. The Round Sword
A strange weapon, perhaps designed for gladiators or berserkers. A sharp circular blade attached to a handle. The weapon deals 2d6 damage on a hit, but on a critical failure, it automatically deals 2d6 damage to the wielder. Leather armour provides no bonus against this weapon, but it cannot deal any damage to someone in chainmail, plate, or dense fibrous cloth (it clogs the blade).
19. White Paste Bombs
Paper tubes with metal tips, filled with foul-smelling white goop. The goop hardens into a rubber-like paste in 2 hours. The paste can be cut, but it cannot be burned or washed away with water. It can clog locks, ruin clothes, or distress animals. The tube can be thrown and bursts on impact.
20. Distance Detector
A small box that fires a red beam of light from one side when a button is pressed. The box then displays the distance (in runes, but it is easy to translate the runes into sensible units like rods and cubits). The maximum range is 500'. If the box is placed against a wall and slowly moved across, it has a 1-in-6 chance of detecting a hollow space or secret door.