One handy feature that most Android devices have nowadays is USB OTG (On-The-Go). Using an OTG converter or cable, users can directly connect external keyboard, mouse, game controllers, storage drives and even external hard disks.
Last year, there was quite an outrage when it was discovered that the Nexus 4 does not support USB OTG. While later on developers where able to add support for OTG using custom kernels, the implementation was wonky at best and required the use of an external power source. The lack of USB OTG on the Nexus 4 was because of the modem being connected to the device over USB.
Thankfully, the Nexus 5 has no such issues and fully supports USB OTG right out of the box. This means that you can easily plug in and use external keyboards, mouse, DLSR cameras and more. While external HDDs are also supported, only the FAT32 formatted ones will work right out of the box. To read/write to NTFS partition, users need to use either a custom kernel or use an app like StickMount that requires root access.
Anyways, the inclusion of USB OTG on the Nexus 5 should please a lot of potential owners out there. It also opens up the possibilities for some serious DIY projects and hacks.