download only the stuff you need from apple's new combined IPSWs
Since iOS 10, Apple have released new IPSW formats which support more than one device per file. These are cool, but most people only want to download an IPSW that works for their device. ipsw-lite allows you to do just this, potentially saving you megabytes (or maybe more) of data!
run ./ipsw-lite --help for instructions
I tested this once, it might not work properly :P. If your device is bricked, turns purple or any other weirdness, I'm claiming no responsibility (i'm not a lawyer though so please be careful when using it).