Mid 1980s-early 1990s UC mobile suits, particularly Zeon or Zeon-styled ones but (and this is the important part) sculpted in a way that is faithful to the original design. It doesn't mean much if they produce a model of a design I like, if they didn't actually follow that design... (MG Gundam GP01, MG Zaku F2 for instance) The result is like going to see a Matthew Broderick movie because you like Godzilla.
Some MG kits are much better than others in this regard. But if they were to announce tomorrow that there'd be a release of, for instance, a MG Geara Doga... With their expertise at producing robot kits that should be fantastic news. Given that I really like the Geara Doga, I should feel completely comfortable pre-ordering the thing as soon as possible, entirely confident that I will like it - because it's a model of a design I already know I like. But with Bandai's habit of redesigning everything, I can't make that decision with confidence. Instead I have to wait to see the end product and then decide if I like it...