A LG Optimus Speed. I think it's name in the rest of the world is Optimus 2x. It was "the first Android phone with a dual core CPU", as LG claims.
It's an
amazing phone, ruined by horrible LG software

First of all, it was stuck on Android 2.3.4 for a long time. When Jelly Bean was released it finally got the update to ICS.
But both GB and ICS had a
shitload of bugs. When I first got it everything was ok. Sluggish but ok. When I installed the update to 2.3.4 it randomly kicked me out of the network multiple times per day, making it extremely unreliable as a phone. Rebooting took 5 minutes which made getting the connection back a massive chore. And the battery lasted for about 12 hours on
standby.
It also crashed and froze all the damn time. It even crashed when I charged it some times.
I was SO disppointed and pretty much didn't really use it for about 2 month.
But then I looked into flashing a new OS onto it. And hey guess what! ICS was already available for it MONTHS before LG released the official update! XD So I flashed it and everything worked beautifully. Some features like the WIFI hotspot didn't work yet and GPS navigation was spotty at best because the CM version that I flashed was still in development but at least I could actually use the damn thing again! And new features were added on a daily basis.
The community behind this phone is MASSIVE. And rightfully so! For a 2 year old phone it is relatively powerful and the screen looks sharp and clear.
The unofficial support for it is actually so strong, I got the update to Android 4.2.2 about 1 month before the Galaxy S4 and all features are working now.
It's just starting to bite the dust now...