Kelvin’s sublimate got a nice new icey bubble surrounding the core ball, that much has already been brought up here. I also think the “clinky” and “windchime-esque” noises that the snow fields generate (the helix at level that changes Sublimate to a slow) were added with the WU. Maybe I didn’t notice them before but that’s what I think.
Montana’s ultimate helix, Big Payback, got a timer that you can see on screen (consisting of a bomb and Montana smiling) so you know when you’re going to explode. However, since this was in the patch notes, I wouldn’t consider this “hidden.” But he did get little fx for his quick melee, like “pow” and “flick” written/shown in comic book onomatopoeia style. Believe that was added with his new op. Still, close enough to WU.
I think Rath’s swords (and maybe other stuff) glow depending on the helix you take at 5. Think I just never noticed that before the Winter Update, I dunno.
Note: Aesthetics includes visual and sound effects.
So what else have you guys found?