Intel Core i5 3470
When applying an OpenGL workload to the Intel integrated graphics, via using the open-source Nexuiz game, the i5-3470 was operating around 49°C, the i7-3770K at 50°C, the i5-2500K at 46°C, and the i5-2400S down at 41°C.
The system with the Core i5 3470 installed was burning through 64 Watts of power when using the HD 2500 graphics.
When looking at the performance-per-Watt while gaming with the Core i5 3470 and its HD 2500 graphics, the CPU came out right ahead of the i5-2500K with its HD 3000 graphics, well ahead of the i5-2400S with its HD 2000 graphics, but noticeably behind its i7-3770K sibling with HD 4000 graphics.