The 3-or 4 in ninja geiden 2 that dumb worm thing in the tunnels...still cant figure it out,,...their are many other just cant remember.
Ragnaros, from World of Warcraft. Probably my favorite boss out of the entire WoW series, as well as my favorite raid. Twinrova from Legend of Zelda: Ocarina of Time. I'll add more when I think of some other ones.
The best boss battle had to be in Twilight Princess when Link and Gannondorf have an epic sword fight at the end of the game. Also, Dark samus or Rundas in Metroid Prime 3 were good boss battles.
That's probably the worst boss battle ever imo, it's really hard if you don't use the Scyth and spam the ultimate technique (which is hold Y). It's really, really, really hard to try and get him any other way.
the giant bird thing from twilight princess when u have to grapple on to its back and repeatedly stab the crystal thing