Paranoia, slipping into mental derangement, and just experimental bizarre stuff, etc
The closest things I know of to give as points of reference are Hexentanz, Naked City and Gnaw Their Tongues but there must be stuff more intense out there. There might be a lot of what I seek in the noise and power electronics type genres but I know barely anything about them.

If there is anything that has demon sounds effects that is cool, or other dark fantasy type stuff.

Here's something I found that would be really cool to find more of, especially a more intense variety (maybe a slaughter or something):
http://www.youtube.com/watch?v=6-KWL20u ... re=related
It's like an ambient soundscape that lets you form a story around, like you are actually walking through a forest and coming across these things.

these may be a bit obvious, but anaal nathrakh or portal?

If you like Naked City I guess you've heard of Fantômas!?

impetuous ritual
http://www.youtube.com/watch?v=eZ3q9O3HVcU

Infester. when you listen to their music, you can imagine yourself in the same hellish cavern that's on the cover. the music is definitely evil sounding, and the vocals are completely inhuman. the right mood can make the music very unsettling.http://www.youtube.com/watch?v=KidpyT1WTto

The SymPhony Brothers: An avant-garde "group" of two people, Sym and Phony. Phony created all the music on Sym's computer, while Sym held Phony hostage with a gun.

They made an album in 1991 called "The SymPhonyic Chronicles: A Tale Of A Man Gone Insane". It's an instrumental concept album, with lyrics that were never vocalized.

https://www.youtube.com/playlist?list=P ... ature=plcp

That's the playlist for the album, and it contains the liner notes on the right side (which has some more info)

Two of the most extreme bands I know of are Darkspace and Disembowelment. Although not necessarily bizarre they somewhat fit into your request. And since you ask for music of any genre you might enjoy them.

Obligatory Thoreous and P.H.O.B.O.S.

Aakon Keetreh's "Dans La Foret" seems to be right on track with what you want. It can be a bit tough to get into, but the full album is the best of this type.

You may also like Diseased Oblivion's "Portals to Past and Present", it is black metal with a doom feel and a lot of somewhat harsh, ambient noise spacing out the metal parts.

You could try Dead Neanderthals for crazy jazz/grind somewhat akin to Naked City, and also Dragged Into Sunlight are pretty insane/twisted sounding death/doom.

Or any LLN band, for that matter. Some of them are just flat-out bizarre; not only the music, but the names, which are often times unpronounceable.

Just lately I've been getting into Aluk Todolo, a French act featuring ex-members of Diamatregon and Vediog Svaor. Their music is a bizarre hybrid of noisy hypnotic Krautrock filtered through post-Black Metal atmospheres, which I reckon should fit your bill nicely.

http://www.youtube.com/watch?v=eTLxY0KVzn8
http://www.youtube.com/watch?v=pLLtuxsjyTY

Check out Skinny Puppy's Last Rights album.

Oh and Dissecting Table.

I only have Ultimate Psychological Description II though.

Threnody to The Victims of Hiroshima by Krzysztof Penderecki

http://www.youtube.com/watch?v=uzOb3UhPmig

and The Axis of Perdition:
http://www.youtube.com/watch?v=AH3T5exg35k

This. There also a handful of Noise artists like Prurient, and Maurizio Bianchi that are worth looking into.

I'd recommend Suicide Commando and Wraith Of The Ropes, awesome shit

Colossus of Destiny - The Melvins
an hour long recording of them just fucking with their equipment in front of a crowd of people.

Check out Striborg. One-man black metal band from Tasmania. He literally lives in the wilderness. Anyway, here is one of the songs called "Solitary Bewilderment" It's weird.

http://www.youtube.com/watch?v=DJ3tGWt7yGc

Also listen to "Abgzvoryathre" by Moëvöt. One of the infamous LLN projects from France. It's probably one of the most bizzare dark ambient albums I have ever heard.

Sounds like Dark Tribe (the German one) is what you're searching for. Bizarre riffs, barbaric drumming and the vocals, which are the most deranged and insane sounding i've heard.

http://www.youtube.com/watch?v=C-rMohR5_LY

You ought to check out RIO (rock in opposition) prog like Univers Zero and Present.

Skuggeheim.

Just finished recommending Void to someone who was looking for cold, creepy music in another forum... My intuition is telling me that you would absolutely LOVE them too. Very out-there, bizarre, innovative stuff. Highly scary too I might add. Heard their stuff high a few times and couldn't listen all the way through.... felt like i was being dragged into an abandoned factory by melting statues that wanted to do God-knows-what to me.....

Yup, pretty weird stuff I'd say.

http://www.youtube.com/watch?v=siuQwMDVpJI

One EP http://www.youtube.com/watch?v=_kBZe4rTK4Y
Planet Aids, I love this song, its what really opened the doors for me as far as noise/drone goes but sadly, few others have matched their intensity.
I'll also rec Black Crow King and on an even lesser note Noism
EDIT you know what check out Last days of Humanity too not so much a journey just the most fuck all noise you can make with manmade instruments.
Hell most of my fav bands came from this thread here
viewtopic.php?f=11&t=88043

This bears listening too,
http://www.youtube.com/watch?v=a8XYpe3s0-Y

Continuing in that vein:

Mitochondrion
Esoteric

Killer track, gonna listen to more of theirs at some point.

I know I've already posted but, another project has come to mind which is Darkspace. It's atmospheric black metal with outer space as a main theme. It is one of the few bands I would describe as genuinely scary, especially if you listen at night alone looking up at the sky.

The project is dark as Darkthrone's 'Transilvanian Hunger', heavy as Sunn O))), merciless as godflesh's 'streetcleaner' and grandiose like Emperor, but more extreme than the four added together. You really have to listen to them to understand, it's indescribable, but to be honest it's quite tiring to listen to a whole album of this madness. The links below are a couple of their slower tracks to start. I think 1.4 or 3.11 are good examples of the more intense sound.

Dark 3.14 http://www.youtube.com/watch?v=uVGUjSHQmlA

Dark -1.0 http://www.youtube.com/watch?v=i32NaNB6p-k

Silencer - death - pierce me

I believe the singer got committed to a mental hospital at one point.

Also, acid bath.

For some reason, this screamo pg. 99 to me (note: not a metal band): http://www.youtube.com/watch?v=RIasrZSDq98

Blood Revolt - Indoctrine

IMO that whole album to me sounds exactly what it would be like to be in the mind of the clinically insane. The fact that A.A. Nemtheanga provides the vocal insanity makes it a must listen.

Wow really, no Khanate yet?

http://www.youtube.com/watch?v=TQZ7_fyju3M

At The Gates - The Red in the Sky is Ours

DARK TRIBE!!

Seconding Khanate. Heavy-ass dirge-y doom that constantly sounds "on the edge" and "broken" almost--like it's only being held together by hot glue and masking tape and any second could collapse into horrifying disarray.

That album is quite comical, Nattramn sounds like a possessed Punch and Judy. Musically, it's quite a decent album though. I think something by Trist, Xasthur, Gris or Wedard would be a more fitting option from the DSBM lot, just my opinion though. That aside, if you want even more miserable music you could also try Nortt, especially Ligfærd and Gudsforladt.

I must say the A-side to Disgrace to the Corpse of Sid by Sore Throat. Sounds like a god awful car wreck.
Fear of God (grindcore band) is fucking horrifying sounding. As Statues Fell is terrifying to listen to at night in the dark by yourself.

Seconding Dragged into Sunlight and Infester. Demilich would be too obvious I guess. Also check out Devil Doll. Not really heavy but bizarre as hell.

One I can think of is the track "Martyrdoom" by Dead Congregation from their album Graves of the Archangels.

A few suggestions:

Prurient - The History of Aids: Blistering harsh noise. It's the most intense Prurient album, at least of what I've heard, and would probably fit the bill.
Woods of Infinity - Hedjå: Insane black metal with disturbing pedophilia themes. There's something unhinged about the music and when combined with the lyrics, it provides this perfect mix of depravity.
Nicole 12 - The First Dance of Spring and Playground / Lolita Love (though any Nicole 12 release works; the split/collaboration with Taint, Candyman is pretty great, too): Nicole 12 is pedophilia themed death industrial/power electronics by Mikko Aspa of Clandestine Blaze/Grunt/Deathspell Omega/Clinic of Torture/etc. It's generally very dark, brooding and disturbing but also has intense moments like the song "First Dance of Spring". Great stuff.
Ash Pool - Genital Tomb and World Turns on its Hinge: Rape and torture themed black metal, with disturbing lyrics and a passionate, destructive sound. Made by Dominic Fernow of Prurient and the guy from Alberich.
Sutcliffe Jügend - Blue Rabbit and When Pornography is No Longer Enough: Blue Rabbit is disturbing dark ambient, while Pornography is a power electronics concept album about a serial rapist/murderer. It's only 30 minutes long but can be hard to get through because of how damn noisy it is.
Abruptum - In Umbra Malitiae Ambulabo, In Aeternum In Triumpho Tenebrarum: An hour long improvised black metal track. Pretty insane but not to everyone's taste.

If anything else pops to mind, I'll post more.