The most luck I had so far with multiple respins and amazing features was on slot Flowers. Yes I know, funny slot but I like it. It is one of those slots which doesn't really give megawins and multiple free spin respins (lol) on a regular basis... but when it does, oh baby when it does!!!
Recently I also discovered the slot called atlantis world which gave me quite nice combos in the feature spins. While I am at it, let me just ask really quickly - does anyone have experience with this slot or the provider GameArt in general, since I can't find almost anything about them anywhere. I guess they are new...