sneak attack with a bow and continue to engage at range with bow until it dies and hopefully its weapon of choice isnt a ebony bow....still say a giant with a wabbajack would be the ultimate boss.

Paralyze him and use destruction magic.

I'd conjure two over powered Dremora Lords, cast a shielding spell, and pop a couple of fireballs in each hand. After that, as I walk into the fight I chug various stat boosting potions then do battle.

Depends on what character I'm playing, what kind of boss it is and what my environment is like.

Such a vague question is kind of like saying "You walk into a store, what do you buy first?" Well, what kind of store? Who am I playing? How much money do I have?

I'd do what is appropriate for that character in that situation to kill the boss. I don't have issues with 'Melee vs my mage' because I plan out and compensate for such an event.

make sure everyone in the cave is dead, by stealth kills or straight up fights. Then depending on the boss, stealth kill him or charge in with blades swinging. Depends on the mood I am in.

Since bandits have terrible loot I sneak past all of them, then attempt to sneak past the boss and snatch the Quest Item (assassinating them if it's on their body). If I fail my sneak at any point I dual wield my Dragonbone swords and dice up whatever enemies I can't avoid (doing a flurry attack will kill a dragon priest in one go) and hide back in the shadows as soon as possible.

As I said, in a cave. Any normal cave. The boss would be a Draugr Deathlord. To me, who it is, where it is, doesn't really matter. I'm interested in other's battle styles. If more than one, say so. I'm all ears.