Microsoft has released a new Lumia 435 recently.
It should be coming out soon (however this might be depending on the country you are from).
If you want to get a 4 inch phone I would probably consider this one.
The reason is that it has 1GB of RAM (compared to the 512MB all the phones mentioned in this thread so far). This makes it a bit more future proof in my opinion especially considering that at the end of this year Windows 10 is released.
I know MS said that every phone running 8.x will get Windows 10, but they also said that especially the lower end ones will miss features.
I got myself a Lumia 730 recently. Bit bigger, but the best phone I ever head
