Which did you like the most, and why?

Good battling, good grinding, Hinox

there's only like 5 right?

The molduga is definitely the best one because just hurting him takes a lot of challenge. Dodging his underground attack can be hard. It's really cool to charge up your flight power and just go in the air and freeze time while shooting him in the mouth with bomb arrows.

Honestly all the mini bosses in this game get repetitive and aside from a few I don't really know how to use the materials for some of them like the Lynel's(which are ass). I think I used a Hinox item once but i don't remember what for.

The guardians can go to hell... they can go to hell and die.

I originally hated the guardians because they're damn near one of the first enemies you see and they 1 shot you. But once you get good at handling them, you feel like a true badass. Molduga's music is Godlike though.

Electric keese.

I too have a hard time picking between Guardians and Molduga; both are badass and exhilarating to fight.

Talus and Hinox are a little less awesome, but still fun.

Fucking hate Lynels.

I'm going to go with Stalnox, only cause that was the first one I met, and it was a really intense battle.
Really wish there had been more mini-bosses.

Definitely the Guardians. They're intimidating just by their song, extremely difficult (you know, without ancient arrows) and satisfying. Though having only one attack is lame.

Second would be Talus, since they're almost a SotC boss.

Lynels.

Most satisfying part of the game was fighting them at Hyrule Castle, dodging their attacks, then completely going ham with the Master Sword.