I like electric city bikes that don't look like an obvious electric bike. Most of "the look" I want involves hiding the battery so it's not some huge lump on the frame.
A few builders are trying to accomplish this by building the battery into the downtube or under the rear rack. It's better, but you can still tell they're electric bikes. Here's Gazelle's page of bikes. And the most expensive Trek e-bikes do the same thing. I'm focused on city/commuter e-bikes because I think that's where the largest market exists.
Here are a few stealthy e-bikes in no particular order:
I tend to like the belt-drive bikes, as do the builders of stealthy bikes, it seems. The Propella is questionable on this list, but in real life, the battery looks more like a large water bottle than a traditional e-bike battery.