Hoover S3607 PowerMax Canister
Most infuriating vac I have ever had my hands on!
I hated the wand and tool system, where the tools insert into the wands (instead of slipping onto the wands, as every other major manufacturer does), locking into one fixed, unchanging position, so you couldn't swivel a tool to get at something tricky.
I detested the wiry, hard nylon bristles on the dusting brush, which might have been very good for cleaning a barbeque grill, but which left little micro-scratches all over furniture finishes.
The upholstery tool had little rubber fingers that hung up on any kind of upholstery with a nubby weave; I had to use the dusting brush on upholstery.
The tool compartment's latches broke soon after purchase, and I am careful with things like that.
The weirdest part of the design was the suction control, which was located in the wand, not in the hose itself. That made using a wand mandatory when you needed light suction. Vacuuming lampshades was a strange, arm's-length process.
And the power cord for the power nozzle was designed so that it dragged the floor where it came out of the PN head. The insulation on the cord kept wearing through. After about the fifth time this happened, I trashed the vac. I normally give unwanted items to charity, but this bad boy got disabled so that it would never work again, and then trashed. The poor have enough troubles without having a vac burn their house down!
This came on top of a Hoover Dimension canister that blew a motherboard; Hoover wanted a fortune to fix it (which it did not get, trust me!).
I've since become a firm believer in the simplicity of Luxes and TriStars.