What is your favorite boss from a Video Game and what is your Least Favorite boss from a video game and why?

I'll keep my answers simple by answering in the same game (which happens to be one of my favorites): Shadow of the Colossus. What's even better is that this game is essentially nothing BUT fighting bosses, heh.

My favorite would be the fan-favorite, which is Dirge, but in terms of wanting to go back and redo the fighting, Gaius really leaves a fond and devastated mark on me. I just love the idea of two swordsmen fighting in a closed arena, and it is so fun trying to outsmart him and trying to climb up that gangly body.

My LEAST favorite would have been Celosia (STOP CHASING ME) but I would have to say it is Basaran simply because of how darn frustrating it is to uproot the jerk and topple him enough to actually take a few swings; he's the one I've died to the most simply because of how stubborn he is in terms of pursuing me.

My Favorite Boss From A Video Game Are

Bowser
Dr. Eggman
Ganondorf
Gruntilda
King K. Rool
King Panther
Thorn

My least favorite is actually from a playable SNES game on this site called Gundam Wing: Endless Duel. It's based off of the Gundam Wing anime, so the boss is Zechs Marquise AKA Milliardo Peacecraft. His Gundam, Epyon, is the most overpowered mobile suit in the game. Heck, I didn't remember it being that powerful in the TV show. I love and hate that at the same time because if you're not skilled at the game, it could take multiple tries to beat him. However, once you unlock him, you'll have fun fighting against the other pilots and their mobile suits. On the bright side, the track that plays during his fight is good, in my opinion.

Favorite bosses are from the Pokemon series. It could be the Team Rocket/Magma/Aqua/Galactic/Plasma/Flare bosses, but I'm referring more to the champions. Red/Blue and Lance are favorites to most people because every kid back in the day fought these guys as their final challenge before beating the game. For these reasons, they are classic. Some of the newer champs like Cynthia and Iris are good, too.

Most favorite is definitely Xemnas' fight from Kingdom Hearts II. It's HUGE, and has tons of buildup to it, and the battle itself is AMAZING!

My least favorite is... Leechgrave, from Kingdom Hearts 358/2 Days. It is the WORST. FIGHT. EVER. Cheap attacks, tons of defense, and moves that can hold you still while you take damage.
Not to mention poison gas... That boss sucked so much!

My favourite boss is Sigma from Mega Man X2. It's so much fun avoiding his attacks and sticking back, especially when you're not using his weakness. It's a great balance that not many bosses manage to have.

My least favourite boss is Charlie MacDonald from No More Heroes 2. I know some people really like his fight, but i just can't get into it. It's so dull and repetitive that it's hard for me not to fall asleep during the fight.

uhhhh am I the only one that LOVES the slime mobs in Minecraft?  Not only are they ridiculously easy to kill.... not only do they cause negligible harm... but they are sooooo darn cute!  And they sound cute, too!  If I could have every mob in Minecraft replaced with the slime monsters... I would

Hopefully that counts as a 'boss', because I don't play many video games.  
I mean, I guess it's not a boss.. but it's a bad guy, at least.  

Singelli : Totally not a boss. But you gotta love 'em, they're adorable.

I have to agree with Drak, Xemnas is easily the best boss battle of all time. Kingdom Hearts was completely full of awesome boss battles, but Xemnas just barely beats Sephiroth. But which Xemnas battle is the best? One battle people forget is the battle at Memory's Skyscraper (the one where you fight him in his cloak). But that's certainly wasn't the funnest, no... The funnest was his final form in that dizzy black and white place.

The worst boss battle though? Tough to say, most battles are fun. Tabuu from Brawl sucked and was only cool because he was a naked deity who had freakin awesome wings and radical attacks. Awesome concept, but really boring boss. That doesn't make him the worst, though, certainly not. The Super Mario World and Super Mario 64 boss battles sucked, but of course there are system limitations. Pokemon boss battles aren't even boss battles because you can't lose and if you're fighting the champion or the elite four or whatever they aren't bosses either because you're fighting stronger enemies. There isn't a worst boss battle.

My favorite in megaman x, would be storm eagle as his design and level and fight are all amazing, my least favorite would have to be launch octopus who is the exact opposite of storm eagle in every way (but both their weapons are awesome, storm tornado is an overpowered attack, and homing torpedo is a decent damaging homing attack.)