My least favorite is the boss from Hera's Tower in Link to the Past, Moldorm, the annoying death worm of spaziness, that pushes you off the stage so you have to fight him and his random movements again. It's like he's dancing to something we can't hear.
 So, what's your least favorite boss?

My least favorite boss is the one where you toss bombs into his mouth that's pretty much all you do what's the challenge of that he's to easy to be a boss

The most annoying boss ever was the Swamp boss from Majora's Mask, it was really tedious trying to get around him. I must say that it was overall fun, but it got frustrating after a while since it was my first time playing the game.

I'd have to say the boss I mostly dislike is Twinrova. They're two ugly hags on brooms flying around, they're laugh is really creepy. And when they fuse for the 2nd phase, it's just disturbing.

I seriously hate that big one with the eyeballs in Link to the Past. You're trying to snag the floating eyeballs and smack them, but at random times the stupid thing shoots lightning that takes up at least half the screen, and you have to try to be on the right side of the screen. I found it really annoying.

  Definitely Moldorm from Link to the Past.....I can't count how many times I fell off that damn platform you fought him on in the Tower of Hera (Probably around about 1 Million times I fell off)

I think that the most annoying boss is Gyorg from Majoras Mask because he swims very fast. Even with the Zora Mask on, Gyorg can catch up with you. Also, I hate how he spawns the little fish that do damage. To top it off, he is hard to hit.

The Link's Awakening Moldorm fight was more annoying. You can only have three hearts of health, so three hits and you're dead.

Has to be non-other than the annoying piece of work,
Moldorm from the Tower of Hera,
It constantly knocks you off the small platform...
It is seriously my most despised boss in the Zelda franchise.

I really was annoyed by moldorm, but after I got the hang of it, it wasn't as bad. One boss that I hat just because of the pure creepy-ness of him is Girahim from Skyward Sword. If you haven't played it yet, I won't spoil anything... But I still call him pedobear xD

I really hated fighting Phantom Gannon in the Forest Temple of Ocarina Of Time, it drove me crazy trying to figure out how to beat him with him coming out of random paintings and stuff lol.

I never really had that much trouble with Legend of Zelda bosses before, though I can't really say that now, still needing to play some of the more recent games, namely Skyward Sword, but my most annoying boss is definitely Morpha. For some reason, despite being what is a seemingly ridiculously easy boss, I could never beat it without using a fairy, and even then, almost dying again. I tried to follow how to videos of the boss fight, but that never helped. Whether I play my N64 or 3DS version of the game, he's one of the bosses who gives me the most trouble.

I've never actually seen Moldorm, so I can't really comment on that.
I think that the most annoying boss is probably Morpheel (3rd boss from the water temple in Twilight Princess). I hated how you had to float up because the bottom was too low but if you went too close he would inhale you. It was so annoying. I also messed up the settings on my wii so that the z-target button wouldn't work properly (my fault), so I had to time things perfectly. At the beginning, he seemed so harmless and pathetic. Then, when the entire thing came out, I couldn't help but think overkill much. Ghirahim (in Skyward Sword, 3rd time) was also really annoying. I would slash and slash and slash about 20 times and only push him back a few steps, and then he would do dome kick that blasted me back off the platform. Then he would do that weird, creepy laugh of his and lick the lips he didn't have. Who comes up with these things?

i forgot his name but its the guy with a lot of eyes from Minish Cap. he sucked

  Shadow link on Zelda 2!!!!

I think the most annoying boss I have ever encountered has got to be the Prehistoric Turtlesaurus. People have probably never heard of this boss because it is from TMNT IV: Turtles In Time. This boss is very annoying because all he does is roll around and drain half your energy with his spikes and then you die within a minute. Even with 2 players that boss is impossible without losing 2 lives or more. But once you overcome the monstrosity of a boss, you will have a much easier time with the game. I guess all good games deserve one annoying boss.

I hate all the bosses that are almost imposable to beat, so the bosses in most megaman games.