I had some follow-up questions so I decided to play the original again. Here's what I found:
The hookshot ledges onto pots, bushes, small rocks, trees, torches (either 16x16 or 16x32), signposts, chests and small items.
The hookshot does not ledge onto frozen enemies, switches, those poles you can hammer into the ground and key items like heart pieces.
Upon closer look the hookshot is a lot more complex for me to do then I figured so I'll leave some aspects for later. Ledging onto trees, torches and signposts will have to wait till I have made more progress on each of those things. I also feel the character should be able to pull key items like heart pieces towards him (like a lazy ass). That'll have to wait as well. The rest I should be able to do. Hopefully today.