This might be old news to some in the Overwatch community (it's a surprisingly tough subject to google) but Kotaku UK reader DANZIGLIVES has discovered that d.Va can kill opponents with a well-timed mech summon. In Respawn's excellent Titanfall, as the name suggests, this is a relatively common tactic.
Here is DANZIGLIVES showing Zarya who the boss is.
It wouldn't be Overwatch, of course, without one crucial detail: this didn't even get play of the game. I'm sure that the Bastion player really deserved it.