Biggest hidden gem coaster?

High five!

^^ I personally steer clear of any parks that are full of micro-aggressions.

Quicksilver Express in Charmland USA, er, Gilroy Gardens. :)

Listen, I love Lightning Rod and all, but Thunderhead is probably my favorite coaster in the park.

….and Blazing Fury…

The Legend at Holiday World doesn't get the praise I think it should.

I think White Lightning is one of the best rollercoasters in Orlando :)

Tornado at Strickler- I mean Stricker's Grove is definitely a hidden gem. It was a huge surprise when I finally got to ride it a few years ago. The park is only open to the public a few times a year, so it's not easy to get a ride on it. It blew me away. So much fun!

Night rides on Adventure Express and Top/Flight/Bat at KI. They're both great at night, even if AE is a bit bumpy. They get completely overshadowed by Beast and Mystic Timbers. Also, speaking of KI, catching a ride on Diamondback during the fireworks show is pretty awesome.

The Legend at Holiday World doesn't get the praise I think it should.

it definitely used to in the 90s and 00s along with Raven. The Voyage kind of overshadowed them but people used to rank those the top two wooden coasters in the world.

Grizzly at KD is my choice. Widely hated by fanboys, I wasn’t expecting much when I rode it a couple years ago but I ended up really enjoying it, got two or three rides in. Nice scenery, rode well in the front and the back, just a fun wooden coaster. I’m usually pretty sensitive to roughness and I don’t really remember experiencing much of that on Grizzly.

Yankee Cannonball at Canobie Lake, gives very forceful airtime and is an absolute blast despite its short height.

I’d nominate Cedar Point’s Blue Streak over Yankee Cannonball for that kind of fun. But is it a hidden gem? Overlooked? Maybe. Every once in a while the PBuzzers call for its removal in order to create space. (For what, I don’t know, it’s an out n back…) But what’s interesting is a few of the rides brought up here lately are vintage. Grizzly? Maybe not an antique itself but it’s a fairly faithful reproduction of a famous ride from the 1940’s. Yankee Cannonball is an old coaster from 1930. I might nominate Lagoon’s Roller Coaster, a John Miller ride that recently celebrated it’s 100th birthday. It’s not overlooked by park fans but doesn’t get much attention from enthusiasts. Perhaps that’s due to its overall mildness.
Anyway, I for one am glad that the classics still hold a gem-like quality.

I’m a blue streak fan but, the cannonball is better in my opinion. Especially since last time I rode it it still had buzz bars.

Biggest surprise coaster that I'd not heard much about was Roller Coaster at Vancouver Playland. It's possibly the greatest airtime machine I've ever been on. Actually had some bruising from slamming down in the seat. I love airtime so it was totally worth it.

Another surprise was Le Monstre at La Ronde in Montreal. It looks really cool but was just an ok ride when it had Morgan trains on it. They switched PTCs a few years back and the ride improved a lot to reach awesome status. It just feels more intense and there is a bit of airtime that I don't remember being there before, especially in the second half of the ride.

I'm in Montreal quite a bit but the piss poor operations at Le Ronde are really frustrating and have not been back in awhile

I was totally surprised by Le Monstre (and this was when it had the Morgan trains, I think). A ride that started out fairly tame but got more and more intense as it went along. Good choice.

The park itself was a disappointment and is one that I think would serve the city much better by opening the gates and doing pay-per-ride. They would get more tourists (and probably locals) wandering through, since it's on the edge of a huge city park. For that matter, it would be helped if there weren't a giant parking lot separating the amusement park from the rest of the park. Theme park-style operations in the center of a big city always strike me as a poor choice (see also: Elitch's).

The one that sticks out in my mind is Python at Efteling.

The retracking done by CSM and the new trains turned a typical Vekoma/Arrow looper into something that was butter smooth and really quite fun (and intense!). It really surprised me just how good it was, for a model that basically sucks everywhere else in their original form.

hambone:

Theme park-style operations in the center of a big city always strike me as a poor choice (see also: Elitch's).

Pretty sure that's how it started as a pay per ride thing, owned and managed by the city. Now managed by Six Flags. Not sure if pay per ride makes financial sense but I'd be more interested in returning to La Ronde with that happening. Though most of it is gone now, I love the old World Expo vibe of it. The only thing left from that era seems to be the monorail.

Another underrated coaster is the Fairly Odd Coaster at Nickelodeon Universe it has a three very intense helixes that spin hard. It hauls the entire time and never lets up.

While I know that neither of these other rides are coasters I do find Journey into Imagination with Figment is a very underrated ride as well. S&S screaming swings are great to.

It no longer stands but the Dania Beach Hurricane in South Florida was a pretty good woodie that didn't get much attention. It was in a FEC (Boomer's) that was closed to make way for another outdoor mall. As if we don't have enough of those in South Florida.

Tommytheduck:

If by hidden gem you mean something that very few people even know about, but is totally worth the trip, Dragon Mountain at Marineland Canada. Right across the border of Niagara Falls. It's a very large, old school Arrow Looper that is just so much fun to ride and probably won't exist for very much longer.

That was the coaster I thought of.

Big Arrow looping coasters are usually super rough but the only odd spots on this coaster are between the loops and exiting the first tunnel.

This coaster is a great experience and it’s not because of the inversions. Even though the final inversions are somewhat original (a batwing that exits in the same direction as entry)

The “cavern” station, the lift hill up the huge man made mountain, a helix that spits you out into a dark tunnel and the looong complete darkness 2nd tunnel finale. That second tunnel is one of my favorite coaster moments ever.

As old as it is I was shocked last year how well it rides

Dragon Mountain is really awesome. The park is up for sale so if this is anyone's bucket list be sure to make it up this season to visit.