This is a great idea and an awesome list :)

My two suggestions, because I at least haven't seen them in many decks.

Bog Witch: Turn any card into Dark Ritual and every turn?! This should be played in every black deck ever.

Soldevi Adnate: You can sacrifice your mid-game creatures to play bigger bombs; and continue scaling up. Also works really well as a sacc outlet for stuff like Dictate of Erebos and can be used as a response to removal being played on your big creatures.

I will add Bog Witch, but as far as I know Soldevi Adnate is pretty well known.

I was always a fan of those weird red cards you see every now and then. My personal favorite is Warp World. Another good one is Fury of the Horde. Off the top of my head that's all I can think of right now.

both of these cards are quite well known so I won't add them.

Thanks for your Input anyway :)

Emeria angel and aven mimeomancer are much more well known than warp world but it's ur list

then I'll add Warp World

It's not like I know all, you can talk to me if you disagree ;)

Nostalgic Dreams deserves a spot on your wall.

+1 because I wasted 20 minutes reading this jaw agape :P

Great card, added!

Lethal Vapors is just so funny. sometimes it is a black 4 mana timewalk, and sometimes, if you give it flash, it is a kill spell AND a timewalk!

added

Among Much Coughing: Hidetsugu's Second Rite

Interesting: Check

Not well known: Check

Unique: Check

:P

added

Overabundance

Mana Flare

Winding Canyons

Energy Field

Gravestorm

Mist of Stagnation

Web of Inertia

Shaman's Trance

Search for Survivors

Temporal Distortion

added everything except Mana Flare and Overabundance as I feel that those are either well known or do things that are well known.

but that's just my opinion

Null Rod sees lots of play in Vintage

I guess I should remove it

I wouldn't be surprised if they've come up already, but perhaps Timesifter or Shared Fate? The latter is a bit more well known, however.

I'll add them both

A new one that was brought to my attention recently was Lim-Dul's Vault, there's also Kormus Bell, Safe Haven is a fun card as well.

PreZchoICE1 I'm sure has a wealth of fun cards for this.

I've thought of some more.

Gilt-Leaf Archdruid (the entire cycle of lesser tribal lords from Morningtide, in fact, of which you've already listed Battletide Alchemist), Herald of Leshrac,Eon Hub (quite the combo there, actually), Psychogenic Probe, Psychic Surgery, and Skill Borrower,

I'm going to have to disagree with you concerning Lim-Dul's Vault, Caligula. Granted, I'm obviously somewhat biased on the matter, seeing as how I know about it, but I'm pretty certain that it's commonly known, at least amongst EDH players.

Oh, oh, oh. Panglacial Wurm. That's a fun one.

Also, forgive the typo up above.

I also think that Lim-Dul's Vault is known quite well, I also think that it doesn't really do anything special or interesting.

the rest of the cards are added

Opalescence there is also the reprint Starfield of Nyx but that card is pretty recent. Maybe the Enchanted Evening and Aura Thief combo? I'm not sure how known those two cards are though

Lim-Dul's Vault is a great card in commander, and I dont know how much more known it is than Warp World, Winding Canyons, Willbreaker (who hasnt tried to break willbreaker) or several other cards on this list. Its basically rinse repeat until you find the best five card combination, doesnt seem powerful or special at all.

I don't see Mirri's Guile, Ghostway, Ulasht, the Hate Seed, Stir the Pride, Goblin Festival, Planar Portal, or Goblin Game.

Caligula is right I could suggest lots more but I'll leave some for others.

Well, this list isn't just about cards that are great, it's mainly about cards that have special, rare or interesting effects that aren't widely utilized.

I have just added Aura Thief, Enchanted Evening and Goblin Game for now.

And remember that you can always talk to me if you disagree with my decisions. ;)