You ll probably already know most of it, but here are some unusual things:

Quest For Blood
http://www.youtube.com/watch?v=HPUPAkP12QM
Solefald
http://www.youtube.com/watch?v=yyjWtSKfeHg
Tormentor
http://www.youtube.com/watch?v=xGU-tujeSZY
Caninus, dog death metal
http://www.youtube.com/watch?v=OrocEmhLsJk
Hatebeak, parrot death metal
http://www.youtube.com/watch?v=VzfxdRNsecM
Impureza, flamenco influenced death metal
http://www.youtube.com/watch?v=3VasbzVzY8g
Jumalhämärä, black metal with some psychedelic rock influences
http://www.youtube.com/watch?v=JlFVz0mV_ng

Not all of those I am listening. That animal metal is funny but musically it sucks, Solefald I love, Tormentor is great, Impureza and quest for Blood nothing especial, and from Jumalhämärä only worthy album is Slaughter the Messenge EP imo.

I think Le Grand Guignol and Silencer are weird.

They were FAR better when they were spelled "Desperados" and had Tom Angelripper on vocals.

A common misconception coming mostly from Sodom fanboys. Each of their three albums are excellent in their own way.

Anyway, western themed metal doesn't seem terribly crazy, the two go together brilliantly, as the romanticized old west is full of high flying ideas of freedom, individuality, vigilantism, roughshod honor and justice codes, blasphemy, adventure, even a degree of unspoken spirituality that are all fully in line with a lot of the romanticism we see in metal.

Great recommendations Slavonic, I have actually only heard of two of those (Caninus + Hatebeak). I think my favorite of those was Impureza, fits the qualifications of absurd and unheard of, while still being pretty damn brutal.

Le Grand Guignol was also great, love that tropical, almost Zelda like thing going on.

Desperados!!! Hahaha! That has to be one of the best yet...so comical, Western metal, gotta love it.

I had thought the same, mixing metal with salsa, but I was thinking it with suits more, something by Hector Lavoe, or Ruben Blades, they had a very well worked the instrumentation.

I will like to know, Is there any metal band, that uses some Ska or Reggae elements? Also if there are metal bands that uses funk elements (wah wah guitars, and slap bass)

Rage Against The Machine? OK, a less obvious answer is Farmakon

On the other hand, Here's Ska Metal: http://www.metal-archives.com/band.php?id=68178

Leper (Can) are a ska/black metal/crust/grindcore band and they rock out pretty heavily.
http://www.youtube.com/watch?v=9_DvcCqTbhA&feature

Some crazy stuff:
Primus,
Freaky Fukin' Weirdoz,
Eisregen,
Infectious Grooves.

Diablo Swing Orchestra, it's Avant-Garde metal with a lot of swing/big band influence.

There's also Demonspeed, which is a blues thrash band with a Sinatra-esque singer

Russian Black Metal Rap?

https://youtu.be/vr3HwydF6p0

How about some goregaze?

https://youtu.be/qRrBtFfFI30

Not really the craziest fusion in the thread, but the Russian band Zhab (Жабъ) has more non-metal instrument than "usual metal" ones : bagpipes, flute, violin, you name it.