Seeing how we all found different abilities to be most fun/useful is part of what makes Igavanias so fun imho. There's plenty of flexibility and it's just fun to play around with all the permutations. Personally I used Lightning Doll the most probably, even though I got it later in the game. I kept is as my primary even after beating it. It just looked so cool and had a big area of effect and a nice power to cost ratio.
And like cane mentioned, I really love that it's essentially a 2D action rpg, with a bigger rpg emphasis than might be expected.
I haven't had time to go back and play in a bit, but I'm still going to try and solve the last bit without a guide for a least a little while.
Oh: and I really enjoyed the Popeye arcade game back in the day. Memories...