I loved Tantalus(Sandship boss) because with my not looking up guides, he was the hardest boss to figure out how to kill. I was using bombs at first, to kill the tentacles in the first stage of the boss, and when I ran out of bombs, I ran around for a while trying to use other items until I found out that if you use a skyward strike, it cuts the tentacles, and by that time I was in the third stage of hitting the boss' eye, so the tentacles were whipping out and about really quick. lol
I haven't beaten the game the first time through yet because I'm trying to get 100% upgrades and heart pieces, goddess cubes, etc. So this favorite might change.