Unique, Orginal, or Powerful creature abilities

[PlzBreakMyCampaign]

Screw it I'm just going to come out and say it: I've been a very naughty, homebrewing min/maxer lately.

I'm compiling some of the "coolest" monster abilities around. Its going on a sort of Master Transmogrifist/Illithid Savant on crack. I'm already aware of the usual combos: regen+nonlethal damage immunity, etc. I'm looking for interesting things and (for once) flavorful things. I'd appreciate your help with neat (non-homebrew) examples!

What I have so far:
Skuz's [DragMag352p81] Fluid Sense
Temporal Drake's Temporal Slide
Glitterhaunt's Earth Glide
Half-dragon's HD bump

Keep in mind the abilities are going to get a homebrew power level boost, so don't be shy about suggestions, please.

[Mister Freeze]

I'm fond of Wendigo's maddening whispers. 

[JohnnyMayHymn]

yellow musk creeper(FF?) musk puff & consume intelligence

ethereal filcher's ethereal jaunt

pair earth glide with a fast swim speed and sprint

the gargoyles looka-like-a-statue ability

also, not a monster; but I always found the Bloodwalker(I'll double check the name later) Blood Magus PrC's capstone interesting, he can enter a creature and teleport to another creature and burst out, causing damage if desired
put this on a maggot/leech swarm and watch your players squirm

[liquid150]

also, not a monster; but I always found the Bloodwalker(I'll double check the name later) PrC's capstone interesting, he can enter a creature and teleport to another creature and burst out, causing damage if desired
put this on a maggot/leech swarm and watch your players squirm

I'm pretty sure that's the Blood Magus?

[JohnnyMayHymn]

also, not a monster; but I always found the Bloodwalker(I'll double check the name later) PrC's capstone interesting, he can enter a creature and teleport to another creature and burst out, causing damage if desired
put this on a maggot/leech swarm and watch your players squirm

I'm pretty sure that's the Blood Magus?

yep, Blood Magus, thanks

[TravelLog]

So is this going to be part of a class? Or are you just mixing and matching the normal abilities with homebrew? Because some normal abilities that currently suck could be made quite excellent with fixes.

On a separate note, Formian Queen's 1 mile telepathy is quite nice. And the Rune Hound being able to use scent with magic.

[Felix Underwood]

1 mile telepathy is especially nice with the Mindsight feat.

[phaedrusxy]

1 mile telepathy is especially nice with the Mindsight feat.

I see your 1 mile telepathy and raise it to 1000 mile telepathy. Check out the spellweaver.

[SorO_Lost]

Did someone say True Dragons for their awesome Age=HD thing?
No?
I did!

I like Beholders for their eye rays, and does this help?

[McBeardly]

Disjunctive bite on the spellgaunt is kind of cool if infuriating.

[ZhonLord]

Taunting Haunt, MM V p. 82:
Has a built-in curse it can attempt to hit someone with every time they miss an attack, and it can force a person to say the opposite of what they wanted to 3 times a day. 

We had one of these little guys following us around an entire campaign.  Oh the many, many ruined attempts at diplomacy...

[Ithamar]

I've always been fond of the Jovoc's (MMII) retributive aura.

The Ethereal Defiler (MMV) can shoot a 6d6 eldritch blast as a swift action every round, stacks with any warlock levels.  Not super powerful, but always seemed kind of fun.  Actually gives a monster something to do with its swift actions for once.

Blink Dog's free action dimension door, and you can still act afterwards, is pretty awesome to keep your monster mobile.

The yugoloth in MMIV, Corruptor of Fate, has an awesome ability that makes anyone attacking it roll twice for the hit and twice for damage.  Your foe HAS to take the lower roll.

[Tenebrous Apostle]

I'd like to add the Nightmare's Etheralness and astral projection (su abilities, both of them) and OFC there is the choker's AND Tombmote's Quickness ability. I work on polymorph myself these days so the memories are fresh. Depending on your type I'd like to point out the chain golem's Blade barrier and If you wanna be really really naughty you can see if the Feed\devour ability could slip under the DM screen...

[snakeman830]

A few creatures have Dual Action abilities.  Ex and give double the normal actions.

[zook1shoe]

The giant mushroom guy in Champions of Ruin
Sharn
Barghest feed
Ironmaw's 60ft reach
Spellweaver's spellweaving
Will-o'-wisp immunity to magic
Phane's time duplicates
Lilitu's extraordinary spellcasting
Black slaadi chaos touch
Sithilar
Hive Mother Beholder
Gambol's extra move action
Kyton weaponry

[Tenebrous Apostle]

I will now blow your minds.. The Carnevus's Two tongued (ex) abilty is what I present. The Expedition to the demonweb pits describes it as a special action, not an attack option so I am not sure If simple polymorph would confer it but it's worth a shot since it does not specify which spells of the carnevus It affects. My own mind drifts to the thought of an enthralled Arcanoloth changing into one of these....

[shriekingdrake]

And there is the Meenlock's (MMII) Rend Mind ability, As well as Dire Tortoise's (Sand) Lightning Strike ability.

[DonQuixote]

Sorrowsworn Demon (MMIII) has glorious, glorious Whispers of Loss.

[McBeardly]

If you can stand high levels of cheese you have quickness from chokers.

[Nunkuruji]

Beguiler - True Seeing

I always recall LEoF having obnoxious critters
Curst - Unkillable
Flameskull - Rejuvenation
Metalmaster - All kinds of metal manipulation abilities
Nishruu - Absorb Magic