So two friends have recently gotten different urban or commuter bikes.
Bike sharing: short rides
The main thing about the bikes is, of course, that if you don't care about performance and don't ride far (and don't care about your brain), then the various bike sharing services are pretty good. The bikes fit terribly (they are typically too small since they have to fit everyone), but they are pretty cheap at $1/hour. The main thing though is that you can't by definition have a bike stolen, so they are perfect for short rides, if unsafe because really you should ride with a helmet.
Entry-level Track Bikes
The next up on the list is the simplest of all bikes, these are so called fixed geared bikes that let don't "freewheel" when you stop pedaling. They are first and foremost track bikes that are all about the most performance, but there are also lower cost "fixies" meant for bicycle messengers.
The big advantage of these bikes is that they are very simple with little or no maintenance and also lots of control when you are going slow. They do have front brakes typically but most of the time you can just slow them by staying on the pedals. They are best for relatively flat terrain like say New York City. If you live in a hilly Seattle, then you really want some gears.
So what are some choices for these bikes, well, if you take a look at something with performance, it's not a terrible thing to look at track bikes and find something in a reasonable price range. The good news is that without a gearset, these things are much cheaper. Most are made of steel for "urban bikes", but if you do care about going reasonably fast then a low-end Track Bikes is they are made with stiffer material like aluminum or even carbon fiber. If you do get a pure track bike, make sure that you do mount a front brake as well as that will give you a measure of safety on the real roads.
Here are some choices remembering that not all track bikes are great urban bikes, they have quick handling and they are stiff, so not great for long ride, but still, being stiff and quick isn't such a bad thing if you like a little performance:
Specialized Langster. ($630) It has an aluminum frame and 48x15 gearing plus a carbon fiber fork so it is nice and light. Not bad for the price with the main issue being the need for better brakes. They also have Langster Street which uses bull handlebars so it is more upright listing for $730. If you are in NYC, then Bicycle Habitat has them to try. There is also a $1,000 Specialized Langster Atlantis 2017 that is mainly about the steampunk look but has the same components. They discontinued it so if you can get it for less, then it can be a very good deal.
Cinelli Vigorelli HSL. This is a harder bike to find in the the states, but has good reviews. It is also an alloy bike with Columbus tubing, but supposed to be very nice. Mainly in Europe.