I love how I only look at the OP, and literally all of my contributions were mentioned....sick post, Chris.
For originality...
Riding with suspenders ahem....sagstraps down.
Remember when everyone...everyone...had a dialed rodeo 5 late shifty? Used to see that trick as everyone's go to "style" trick. Now it's the tweak safety or lead uncrossed blunt 180's, or lazyboy 180's. Basically 180s.
Urban rails with lips built so that they're pretty much ride on. Rails setup to be hit on the "outside", or from alongside the steps.
Slope courses used to have one small "setup jump" and they also used to mix in a rail/jib feature much lower, and breakup the jump line. Now, you almost never see a jib after the first jump. Maybe as the last feature, but never in between two jumps.
How about sketchy, hand-shaped 12ft pipes? I honestly think if resorts built small half pipes that weren't ice walls of death that are basically only built if there's a chance of hosting a major comp or attracting "training" athletes, you'd see a lot more pipe style and "progression" in terms of creativity. I know they're a huge effort and cost to maintain, and I guess that's why you never see them.
There's a lot less "novelty" features in parks these days I feel like. It used to be mandatory to have like a school bus, or some kind of car, or just something visually unique that people kind of never knew what to do with.
Really tall, really skinny rollercoaster rails. They used to be everywhere.