Nexus 5 Problems
In the fall of 2014 I switched from my Galaxy S3 - which was a good enough phone except for truly wretched battery life - to a Nexus 5. While generally I've been happy with it there have been some issues.
Having a built-in flashlight feature is great, but as I found out the first time I used it doesn't work as a reading light in a pinch. After about a minute it goes off and won't go back on without rebooting the phone. Around October 2015 I thought this was fixed, but it happened again November 5. It may have something to do with rotating the phone with the light on.
The Google Loop
One day I woke up and picked up my phone and it turned off mysteriously. Plugging it in to its charger it turned on, rumbled, showed the Google logo, and turned off again. It then did the same thing repeatedly for over ten minutes. Looking around online this appears to be an issue where the part of the power switch inside the phone gets physically jammed. You can fix it by stroking the switch top to bottom, flicking it with your finger, or smacking the phone (not too hard). I managed to get it working again and after a few issues over the next day or two it's been fine, but this was worrying.
Wifi Connection Issues
For a long time I felt like my phone didn't perform as well on my home wifi as it did on mobile data - browsing the internet DNS would fail to resolve, or on Twitter images or profiles would fail to load. Looking around it seems that some wifi "channels" aren't actually supported very well - I'd never heard of this happening, but by changing my router's settings I was able to get it working. For a 2.4GHz wifi router (like me) you need a channel of 11 or lower (so not 12 or 13), while for a 5GHz router 36, 40, 44, or 48 should be fine.
I'm worried this will cause issues when travelling, even if just around town, but it hasn't affected me too badly yet.
Directories Show up as Files
This happens when the phone is connected via MTP, the most straightforward way to move files on and off. Searching reveals other people have run into the issue but it's not clear why or how to fix it. It only affects a small portion of my music collection so I've been fine so far, but I really wish I could use the phone as standard removable storage...