The Grind King Bearing Rims provided zero functional advantages to the user, however, they made your wheels look objectively 10 times cooler. The intended purpose of keeping dirt and dust out of your bearings was in vain, as they only trapped the debris in your bearings.
THE Z-ROLLER SKATEBOARD TRUCKS
The Z-Roller Skateboard trucks were intended to solve the issue of wearing down the hangar of your trucks from doing grinds, this was done by having a roller in the place of the metal so you just rolled instead of grinding.
Unfortunately, The Z-Roller Trucks ended up with the same fate of having the opposite effect of their intended purpose, as any imperfection created from grind tricks would make them seize up and grind much worse than regular trucks.
THE TAIL DEVIL
The Tail Devil Was essentially a small piece of plastic with a flint in it so that you would screw into the tail of your skateboard, this was used so that when you would scrape your tail your board would throw sparks like crazy. However this small device would render your board practically useless for regular tricks as it kills the pop of your board completely. Check out Jenkem Magazines article on them here.
The decks from Aircraft Skateboards were made from aeroplane aluminium, with the idea of having a lighter skateboard that was reasonably indestructible from skating it. The issue with these boards was that as the nose and tail wore down it became a razor sharp piece of steel that would actually cut you up and be a serious safety hazard, the board also did not have a nice pop.
PLASTIC SKATEBOARD RAMPS
This one on the list is a blanket for every single brand making plastic skateboard ramps. At a glance, these ramps seem easy to use and affordable, however, plastic skateboard ramps are terrible for skateboarding because they are so lightweight and flexy. Anyone that has tried to skateboard on these ramps can tell you that these things just throw you off your board into the concrete.
POWELL PERALTA BONITE SKATEBOARDS
You may be surprised to see a brand as big as Powell Peralta on this list, but just because they are an iconic legacy brand does not mean they cannot make bad products. These boards had a layer of a tar-paper like material in the board that was intended to make the board both lighter and stronger. In actuality, these “Bonite” skateboards would break much faster and actually swell up super weird whenever there was a bit of contact with water.
Avenue Trucks is the first skateboard truck brand to feature a suspension system, with bold claims that the trucks increase pop and speed. However, the pop from your skateboard when one does an ollie comes from the pre-loaded compression and snap of the tail, and these trucks just end up feeling like a kill bounce on a trampoline for your ollie.
THE LONGBOARD STROLLER
The Longboard stroller is meant to provide a fun way of cruising around the city with your child, however, let's say there hasn't been street cleaning yet and you hit a rock, you would literally fall forward and piledriver your baby into the concrete WWE style. The dangers of this product would have been obvious if there was any actual skaters/borders designing it.
This Product was meant to prevent the age old issue of hitting a rock and falling over on your skateboard. The inventors have failed to realise that any crack or imperfection in the ground will be caught on this glorified cowcatcher and send the skateboarder flying without a rock being present. We have no clue how this product got out of the testing phase.