My personal crowning moment of awesome (note: not awesome in the slightest but it left me feeling super elated, an excessively rare thing for me) was playing Rainmaker on The Reef (also take note, I just got Splatoon 2 and so this was a C- game). Game started, every single squid rushed for that crazy thing, I wind up being the only one to correctly swoop right under the bridge where it's actually located. Start shooting it (I'm using a Splattershot Pro), an enemy player comes down there (can't remember their weapon, all I know is that I either outpaced it or I had already done so much damage to the shield they weren't gonna stop it), I splat the shield and grab the Rainmaker, and proceeded to run that thing the whole way across the map as my teammates leaped the bridge to follow me. I actually wound up running it straight up the ramp and dunking the thing, something that I've never done playing Rainmaker in Splatoon 1 or 2 up until this point. Now, I am an extremely excitable person, and so managing to accomplish this (absolutely incredible feat to my brain) sent me through the roof. Needless to say I felt incredibly cool/fresh afterwards and was jittering so badly that I actually had to turn the game off and take a break for a few hours.
To anyone else who plays Rainmaker I accomplished the most basic thing ever (and the requirement to win via KO), but for me and my skill level (I call myself the Queen of Failure, after all) that was the most exciting thing I've ever done in Splatoon thus far.
Another cool but not so awesome moment for me was playing the new Moray Towers with my trusty Carbon Roller and flipping off of the ink rails for a two splat vertical swing on the enemy players below me (who happened to be focused on a teammate of mine and not the rail behind them. This was during Turf). Followed this up by a two shot fling splat on the third one who was missed by that previous vertical swing. After this I proceeded to ink around... somewhere between 800 and 900 I think by the end of the match. Felt proud of myself given my usual track record.