Well mine so far are
Offence:
Pharah, Here jump jet and hover ability are great because most people are not looking up you can attack with the rocket launcher and concussive blasts nicely. The rockets also mean that aim isn't as critical
Defence:
Bastion, the sentry configuration is quite potent. Self repair is great. Tank mod is kick ass
Tank:
Winston. I haven't played the others so I can't compare. He his fun with is gun, jump and shield. I tend to see road hog every game so it seems like that is the go to Tank
support
I digging Zeny. He has an enemy debuf, ally heal, good offence. His ult can restore an entire team so great in a team fight. His a bit tricky because of aim and the way people move around it's quite easy to buf or debuf the wrong hero
Mercy would be a close 2nd
Need to try lucio