eBay Daily Deals are often good. Sometimes for electronics refurbs and last model items are on the Daily Deals but often new current model stuff too. Got a great deal on my current model phone from an eBay Daily Deal. I buy several 10% off gas cards too when they come up.
(New) hard drives are usually cheapest on eBay.
Lots of traditional retailers have eBay stores as well. I've bought from Newegg's eBay store more times than I can count, for example. Manufacturers also have eBay stores.
There's a lot of room for niche products but it seems a lot less overwhelming than Amazon is with all their private label stuff and poor search results.
Lots of good selection of used stuff as well. Do I really need a new Chromecast? Nope, used is half the price and works just as well and is better for the environment.
I also hear it's a good place to get uncommon sized bras.
eBay has its flaws too though, avoid Chinese megasellers like the plague. Its usually a lot easier to spot a fake or shoddy product on eBay than on Amazon. I've found eBay's customer support to be good when you have a problem and an unreasonable seller.
[1] The good thing about eBay cashback portals is they rarely have restrictions other than giftcard restrictions. Target.com may have 2% cash back but excludes Apple products and Bose products. I've never seen brand exclusions on eBay's cash back through shopping portals. There's usually a 1-2% cash back portal for eBay and eBay bucks are a minimum 2% eBay gift card as long as you have over $5.
This is a flaw with Amazon, not Ebay. Ebay makes the Chinese sellers very, very easy to avoid: you just look at the selection list on the left side, and click "US Sellers only" or "North American sellers only". Voila! No Chinese sellers in the search results. Amazon makes this completely impossible: it's very hard to tell where a product is being shipped from on Amazon, and usually you have to go through checkout to see the shipping times and infer from that.
Recent HN story: https://news.ycombinator.com/item?id=12711353
Go follow the link to techpowerup and you will see 89 comments. Most of them quite negative about the current state of Newegg. The complaints seem to date to before Newegg was purchased by a Chinese company.
Ironically, many of the complaints there say that Amazon is better. Ha. It seems like they all suck now!