Bosses sorted by location:

Infested Sewers, simply strike when you see the big ball open it's eye to stun it. (Hp: 16)

Lakeside Prison, when the snake rears it's ugly head, attack it to render it vulnerable. block it's acid when it goes back below the surface and it should be easy peasy.
you can't stun it as far as i know. (Hp: ~40)

Icy Caves, block his ice breath and commit animal cruelty when he rears his machinegun. (Hp:~81)

Witches Hideout, attack when she fires off her thunder bolt, (glowing ball of lightning) and she will be so shocked that her defensive sphere dissapears. Hit on her now. (Hp:56)

Coal Mines, this one is really easy to do flawless, he will start to pull his drill back so block and when he fires his rocket you simply bat it back at him by attacking. (he is a lot worse at tennis than ganondorf). when he puts his hands upp in the air he is ready to be attacked. do this about twice and he should be dead. (Hp: ~33)

Monastery, the boss will strike twice by reling it's head back (when you see this block) and then the Priest part will start praying, hit him now to dispeal the evil spirits and strike the sinner down (should be able to get a couple attacks off each time). (Hp: ~36)

Mountain Graveyard, The cool gunman will start off pistol whiping twice (he dosen't have one so he improvises with a shotgun instead) strike him back when he reloads it and he will be so embarased his ice will melt and you can hit him without freezing from his cold demeanor. (Hp: ~40)

Zakkum Tree, haven't found any weak point on this one, simply block his vines and pummel him, you can interupt his bite by attacking. (Hp: ~56)

Mages Tower, he has cast weak protection (he is now down 1 colorless mana). Wait for him to attack and show him how to do it properly (a right hook to his unprotected chin when he puts his hands togheter stuns him) Teach him the difference of lifting books and bearing arms (if you did the Icy caves before you might really "Bear arms" if you took a trofy with you) (Hp: ~40)

Sad Village, did not find any tricks for this one, just burst him down as quickly as i could.
(Hp:~140 - 156)

Deep Dungeons Of Doom. have no tricks for this one, (Hp: ~210)

Hp numbers gotten from counting amount of hits for crusader with wampire slayer (5 attack), numbers with ~ are estimated, might be 1 or 2 hp more or for the harder bosses that number or below because the attack were higher and thus less precise.

Normal enemies:

Headless Horseman, less of a weak spot and more off a exploit, hit him a few times depending on agility and block when he rears his horse back and he will simply stand there getting pummeled.