While not 3rd party, I would suggest going for a Canon 430 EX II.. I'm not saying that the third party flashes are lacking, as I have not opted to try them. I have noticed that a number of them are missing features here and there on third party flashes- so I opted out... You might look at the Canon 320 EX as well, but I would think that the 430 EX II gives one a little more flexibility..
EOS 5D III, EOS 7D,EOS Rebel T4i, Canon 70-200 f/2.8 IS II, Canon 24-105L, Canon 18-135 IS STM, 1.4x TC III, 2.0x TC III, Σ 50mm f/1.4, Σ 17-50 OS, Σ 70-200 OS, Σ 50-500 OS, Σ 1.4x TC, Σ 2.0x TC, 580EXII(3), Canon SX-40, Canon S100
Fond memories: Rebel T1i, Canon 18-55 IS, Canon 55-250 IS, 18-135 IS (Given to a good home)...