More Free to Play games tested. All playable.
More info about performance below.

Spiral Knights

Spiral Knights is very simple and lightweight game in Java.
It is running great on all high and max resolution in 15-25 FPS, and on lower settings in 20-30 FPS.
Fun MMO.

Crimecraft BleedOut

Game runs 8-20 FPS, it is very playable but it could be better.
You need to set everything to low, but main problem is that 1024x768 is lowest resolution.
I wanted to edit config files but they are ini files that are not readable (similar to Bulletstorm).

Goto VIDEO
Resolution 1024x768
VSync Off
World detail Lowest
Texture detail Lowest
Shadows Off

Goto ADVANCED VIDEO
Dynamic Lights Off
Bloom quality Off
Particles quality Low
Advanced particles Off

And restart game.

Champions Online

Great MMO, running on 4500.
FPS around 15-25, playable.

This is enough free to play games for now, next time I continue with pay to play games.