I'd say...in no particular order...
-Chandler Stephenson. The guy is the ultimate utility knife. He's like a true Leatherman that just goes to work and does the job. Not some chincy Swiss Army knife that is okay at everything but kinda bad at everything too. He's fast, hard working, genuinely skilled 60pt reliable 2-way Center who can play Wing and meshes with pretty much anyone, year after year. People still act like he's just a 3rd line grinder who got a lucky boost Becuz Vegaz.
-Adrian Kempe. Quietest perennial top line top flight goal scorer with a big noticeable powerful and speedy game. I honestly don't understand how he flies so under the radar. It's not like he's one of those "quiet" players who only stands out on deeper inspection.
-Philip Danault. The above-mentioned "quiet" player who is just one of the best unsung 2-way matchup Centers in the entire league. He's so good. Doesn't typically stand out nor does his steady ~50pts a year, so i can at least understand why he gets underrated. But he's worth so much more than that production.
-Joel Farabee. Also doesn't post the most gaudy numbers in the world on the surface, but he's a bit of an even strength beast, and a real engine on the ice that makes things happen.
-Cam Fowler. Sort of gets lost, drowning trying to carry that Ducks blueline. But he does a pretty admirable job of trying.
-Ivan Provorov. Similar to Fowler in a lot of respects, as a guy who has been dumped in over his head a lot. People have actually noticed him though, and i think way overreacted to it. People actually seem to think he's a "bad" player. When he's actually a very good player, with flaws...who seems to constantly find himself in bad situations that highlight them by expecting more from him than he has to give. But it definitely makes him "underrated" at this point imo.
-Nino Niederreiter. Just the most rock solid, steady as she goes, ~20G - 40Pt winger out there. Just does everything you'd want from that sort of player and without much of any fuss or drama. Basically just the current archetype of an effective, reliable Middle-6 Complementary Winger.