Overwatch is one of my favorite games right now (and has been for a while). And when we were introduced to a lot of these characters I couldn't help but seem to already -know- them. There were some that had obvious references, but the more I thought about it, the more I realized I think it might be possible Blizzard intended to mish-mash characters we already know together to create something new, but still familiar to us. And while I'm primarily referring to aesthetics, some story-wise as well.
1. Torbjorn
Dr. Robotnik/Eggman + Classic Fantasy Dwarf
2. Winston
Beast from X-Men + Caeser from Planet of the Apes
3. McCree
Clint Eastwood (obviously)
4. Reaper
Spawn. African American male mercenary who is killed and brought back from hell.
5. Junkrat + Roadhog
Generally speaking... Mad Max crazy people
6. Soldier 76
Cyclops
I'll add more later, but also give me some of the connections you've all made.
There also are some pretty unique ones. I feel Ana is for example.