Crimson "Valent" Azure 
Husband of Rainbow Dash.
If there's one thing I'm tired of seeing besides some fetishes like foalcon, it's futa. I swear whenever I'm looking for any kind of mare x mare thing I always see like pages and pages of futa. If I wanted to see Rainbow Dash with a penis, I'd look up Rainbow Blitz. And as said by LightningBolt above, sometimes people don't even tag futa properly so I see Scootaloo giving futa Rainbow Dash a blowjob over and over again.