Cats reject most things you buy them. This is not a personality quirk — it's a design problem. Cat products are often made for the human browsing them (cute, aesthetic, human-logic organized) rather than for the cat who's supposed to use them. The things below passed the actual test: the cat used it, kept using it, and didn't abandon it for the cardboard box it came in.
Top-entry litter boxes reduce tracking, eliminate spray on the walls, and are harder for dogs to access. The Modkat XL is the cleanest-looking, most functional version of this design. The lid doubles as a mat (cats walk across it, leaving litter behind), the liner system means you never have to scrub the box, and the capacity is large enough for big cats or multi-cat households. The $70 price is one-time.

Litter is the one cat product where quality directly affects your quality of life. Dr. Elsey's Ultra is a 99.9% dust-free clumping clay litter that forms hard, easy-to-scoop clumps, has very effective odor control, and doesn't track as much as most clay litters. At $30 for 40lbs, it's not the cheapest but it's the best performing. One bag lasts a single-cat household 5–6 weeks.

Most cat toys are ignored after three minutes. The exception is anything that mimics prey movement — specifically, a feather wand that moves unpredictably. Da Bird is the one that trainers, vets, and cat behaviorists consistently recommend. The feathers spin as the wand moves, mimicking bird flight. The replacement feather attachments are cheap and the wand itself lasts years. 10 minutes a day with this toy is the single best thing you can do for a bored, destructive, or overweight cat.

Most cat trees wobble after two months and become unusable. The Go Pet Club 62" has a wide base, sisal-wrapped posts that cats actually use (not the carpet-covered ones they ignore), and enough platforms at different heights that multiple cats can use it simultaneously without conflict. At 62", it's tall enough to satisfy climbing instincts. It's not beautiful but it's stable, which is the only metric that matters for cat furniture.

Cats have low thirst drive and are prone to urinary tract issues from not drinking enough. A water fountain — running, moving water — significantly increases water intake in most cats. The Catit Flower Fountain is quiet, has triple filtration, holds 100oz, and the flower design produces three water flow patterns to attract different cats. It requires a filter replacement every 2–4 weeks ($5 each).

Cats are motivated by prey drive (things that move unpredictably), scent, and comfort — not by cute aesthetics. The products that work mimic prey behavior (feather wands), provide real physical comfort (stable platforms at height), or meet basic needs better than what they had (cleaner litter, running water).
Generally yes. Cats evolved to drink from running water and many cats prefer it strongly to still bowls. Increased water intake reduces the risk of urinary tract disease, which is common and expensive to treat.
A top-entry box combined with high-quality clumping litter and daily scooping. No box will control odor if it's not scooped daily. The Modkat XL reduces smell significantly compared to open-top boxes by containing the litter environment.