From my own research I have to say mattress; also shitloads of traffic. I am really surprised how many small time affiliates are ranking for something with such a high KD of 28 and 34 for the best and reviews version. I can't even imagine how tough that is... I've been trying for over a year to get to the top for a KD of 14, also a "best" keyword and hovering at the bottom of page 2 and top of 3... with crazy swings too. I also imagine microwaves, coffee makers, fridge and vacuum niches are also played out and hard as a mother. I always cringe when i see like 8 amazon niche sites on the first page for some best keyword because i sure as hell dont want to be #9. I prefer niches where i am the only review site on the first page; more likely to get more clicks if yours is the only review. Its weird becuase my KD is 14 and theres only one small time affiliate site at the top, the rest is sweethome, toptenreviews and everyone else is on page 3 and has been on page 3 for 2 years! no one else is moving to the top! The one on page 1 has his own network of hundreds of pbn... but its only KD 14 whereas i see in mattress with much higher kd tons of affiliates on top driving sweethome to the second page... lol so what other niches do you guys think are the toughest in amazon typical "best" home product niches?