I enjoyed fighting pretty much all the bosses in TP, however my favorite boss to fight is definitely Blizzeta.
The Blizzeta boss fight gets bonus points in my book for an interesting setup story-wise, it vaguely reminds me of how, in ALttP, in the Gargoyle's Domain, the boss is actually disguised as a girl locked inside the dungeon, and you have to solve a puzzle to start the fight since the boss won’t drop his disguise willingly. (Fond, fond memories of solving that.)
Anyway, that aside, Blizzeta also has my absolute favorite boss music in TP. Ice is also a theme I really love, the slipperiness of the battlefield, and the sudden mega freeze over of the room before the battle starts, was awesome. The ball & chain was always a fun weapon to use too, this battle was no exception. I think the battle could have been improved though, I was mostly disappointed by the lack of difficulty, and even more so by how short the battle was. That’s pretty much a gripe I have with most boss fights in TP though, and it didn't prevent me from enjoying the fight a bunch anyway.
My runner up would have to be Stallord. It was definitely a more memorable fight overall for me due to the spinner. Playing zombie pinball, spinning up the tower, all very fun. The biggest drawback was that I was slightly disappointed they didn’t implement even more ways to use the spinner throughout the fight, and my above complaints with Blizzeta.