Strongest phenom cpu?

For gaming, the Phenom II 980. Although you may not find those available anymore. The Phenom II 965s from Newegg are basically the same, they just have a lower clock speed. You can overclock the 965 to match the settings of the 980 easily enough.

For productivity work, and, well, to an extent gaming too, the 1075T/1090T/1100Ts are 6 core CPUs also "Black Editions". But they're pretty much gone everywhere unless you pay ridiculous prices on ebay to get one (and I wouldn't)