Generally not a huge fan of mecha so my standards are extremely low, as long as it isn't a horrible flappy mess or completely lacking anything that makes it even look like a giant robot in the first place then it's pretty much fine with me.

Notable mentions to Gosei Great, Dragon Star-Lord, Daibouken, Go-Buster Ace and GoZyuJin. And a nod to Daizyujin as it all began there for me.

Magiking and Gokaioh.

Daizyujin, Dairenoh, TimeRobo, Shinkenoh and GekiTouja deserve mentions too. I also have a soft spot for Jet Icarus because he's my holy grail, but he looks pretty awful, honestly.

BakurenOh, GaoGod, SpinoDaiOh, and, of course...

Wonder Gosei Great.

Oh crap, how'd I forget about him?
Add that one to my list, too.

:lol

When I sat down to list my favourites I was overwhelmed by how many I like. I mean it's not a "lot" by the length of the franchise and quantity of designs but I'm someone who can firmly say they HATE sentai mech action, so it's a lot in proportionate to me.

It's like I didn't even mention the Jungle Fury/Geki mecha as I liked pretty much every single thing about it in that show, other than the cockpits. Which is very true of Kyoryuger as well, minus Gigant who SUCKED. To an extent SPD had great Megazords all the way through as well.

I guess what I learnt is the designs aren't really the problem with the mecha, for me, it's just the execution.

Well Dieren-Oh( The big Dairanger Megazord.) I also really liked Ryusie-Oh's Megazord form, since I like it when individual mechs do that.

Gaoking,Daibouken,and ToQ-Oh.The first because it's from my favorite series and it's such a clean look.The toy version also had some articulation that is rarely seen.

As far as Daibouken and ToQ-Oh,I like them mostly for the fact that I dig "realistic" transformations.Yeah,ToQ-Oh does take some liberties (I.e slamming it's fists down to stand up),but the general combination works in a way that you believe it could actually happen one day.

As someone who really only cares about the mecha over the actual series: Magiking.

Very unique transformation, wings built in to the design, even its sword is a combiner, dragon mode, and just a beautiful paint job (doesn't hurt that I own the Complete Edition). It manages to override my love of cluster final combinations like EngineOh G12 that utilize all the mecha of the series. Also being away from Power Rangers since Turbo, seeing Magiking is what got me into collecting DX mecha (for better or worse).
I also think it's pretty awesome that the individual "mecha" are actually gigantic magical avatars as opposed to piloted or sentient vehicles.

I'm a huge fan of Wolkaiser, as well.

EDIT: And Magiking has a hat!

Great Go-Buster.

The three dino mechs: Daizyujin, Abaren-oh, and Kyoryuzin. I also liked Gokai-oh, Gojyujin, Go buster ace, Gosei Great, GekiTouja, Dairenoh, GaoKing, and Killer-Oh.