Did you know Widowmaker can grapple onto a basketball in flight? Perhaps it's impractical to carry one at all times, but there's certainly potential to suprise your enemies from new vantage points. You'll want to, what with the recent Widowmaker nerf.
And who'd have thought Zarya an acrobat? By putting her particle cannon to good use (with some help from the odd red phone box), PlasmaNapkin gets her scaling buildings like Genji.
I think I'll stick to Bastion.