I really like cellphone changers, maybe because it's the first type of changers I've seen (MagiPhone), especially when they use the regular cellphone mode to transform and do stuff, like in Magi and Gaoranger. The Gaoranger Henshin is so cool, how they put the cell phone to their ear and shout Gao Access!
I also find gun changers like the Gaburivolver and unusual changers like the SP License and the Tensouder really interesting too.
But then again, as long as it has some fancy sound effects and looks cool, I'm fine with anything (though swords are a bit of a problem on the toy size. The Ninja Ichibantou is soooo tiny! ;_;).

The item i like most is Morphin Blaster of Jin/J Beet and Stag Buster.

If someday we have a insect-themed how would be the mechas ?

I would imagine centipede for the legs, have a Wasp for one of the arms, stag beetle for the body and the head, an ant for the other arm and a dragonfly on the back to give it wings.

or at least that is my makeshift idea.

Centipede is not a insect.

Wait really, Okay scratch that idea then.

Okay grasshoppers as legs then.

Pretty sure Toei wouldn't care about semantics.

Yup. Just look at Blade and Kabuto. Insect based shows that have Riders not based on insects.

But they would be mystical or technological ?

Mystical insects? So like take actual insects and grow them to mech size? Or use them to henshin?

Technological is obvious, but the mystical would be neat in this what-if situation.