1. King of Stilwater (Saints Row IV)
Okay, I know this really isn't a bossfight. It kinda has some harder enemies in it but nothing really boss-like. However, I
love this mission. Everything about it is perfect. The music, level, and dialogue. As a rather huge fan of the Saints Row series, this mission also struck all the right notes with me because of it being a throwback to the earlier games.
2. Lawrence Barrett (Deus Ex: Human Revolution)
I don't really like the bossfight itself, but I really like his character design and how he acts. He really seemed like an interesting character but not much was really revealed about him in the game. Only the books.
3. Alcor Class Warship (Serious Sam 3 BFE)
Really fun and has cool music.
4. Shodan (System Shock)
The whole game is practically a bossfight against Shodan in my opinion.
5. Maero (Saints Row 2)
This asshole. You'd have to have played the game to understand how great it is to put a bullet in his head.