Well, my game rules are being tested more and more as my characters advance. I am also working on a number of odd strategies with monsters that often cause strange looks. Some things however I am wise enough NOT to do, but in case you are not as scared of player uprisings -- you might want to give your monsters these Special Qualities.

Neglible Experience Points
Monster only awards 1XP/level.

Hah! Your players just fought a 12th level monster with multiple attacks, a breath weapon, damn thick armor, but you smile knowing that they will be getting only 12XP for their efforts.

DR ALL/Max Damage
Monster can only be harmed if the attacker rolls maximum damage.

Player: "I rolled a seven, so with +5 from Strength, +3 from the weapon, +5 from Power Attack, that makes 20 points of damage."
DM: "The monster shrugs it off."
Player: "WHAT? The mage only did 7 point of damage and hurt it."
DM: "He rolled a four, and that is maximum damage for his dagger."

Virtual Bank Account
Monster has the finances to buy what it needs from the DM. This requires a move action (well talking is a free action, but this special ability does require some thought).

Monster: "Hey, that acid hurt!"
Character: "Hey, guys, acid hurts this creature!"
Monster waits for its turn - Monster: "Hey, DM, how much for acid immunity?"
It is best for the DM to only smile, although stating some astronomical price sometimes does bring pleasure.
Monster: "Good, okay, debit my account and give it to me now."
DM makes note on paper and claims that monster now has acid immunity as he rolls its attack.

Here is another -

Hide in Plain Sight
Monster may make a Hide roll at the end of each round.

Yep, the monster charges towards the fighter, strikes, then disappears. The fighter and others get a Spot check, but if they do not make the DC then they cannot see the monster (even though he right there prepared to make another attack on his next turn). Note that the fighter can attack where he is certain the monster is (although the DM should penalize the player for meta-gaming) with the usual Concealment check for total concealment.

Damage Dispersal
Monsters in groups can disperse damage between themselves.

When fighting creatures with this ability, all damage is dispersed between the monsters in the group at the DM's discretion, regardless of the PCs' or monsters' positions in combat. Typically, damage dealt by the PCs is always assigned to the monster that has taken the least amount of damage so far.

I like the Damage Dispersal idea! And who WOULDN'T want Hammerspace?!?!

huh..alot of these seem wholly based on ooc concepts, though a few of them have a decent idea, they just seem poorly executed and unexplainable. (and no, calling it "magic" doesnt explain it, its just a cop out answer...not that this isnt bad, i mean a few times surely, if it helps with the story and makes things interesting why not...however, its not really fair to the pcs to just create an alternate set of rules...its one thing to say a monster you thought would be more powerful got in a few shots you didnt roll to make it more interesting, or to not pummel the mage who inadvertently got to close to the giant, etc, however...

negligent exp...virtual bank account? where did these even come from? talk about breaking immersion...this is utterly ooc stuff in most cases. I can see scenearios where a villain, with a decent int score and assets could certainly prepare for the plausible, however, if your pcs are specifically thwarted, personally, for no good reason, its not a challenge...its a witch hunt.

this is also piss poor dm'ing. you pretty much saw what they do and ooc, prepped for it. its one thing to have a diviner watch your pcs and prepare for them as best he can, its another to have you troll with an int of 2.5 to have a wand of 'screw you pc's'

as usual, the devil is in the detail. I can see some merit to the others...such as hide in plain sight...depending!!. i had a revamped shadow monster use this ability, naturally, in a room with with heavy shadow...it made for a cool affect to watch it "smile" and fade to black, adding to the mood...having a theif toss a smoke bomb, then giving the pcs a spot check, seems perfectly reasonable as well, granted this also matters on terrain.

as a fun take on dmg dispersal, i cam across a monster with 12 "parts" every time one of the brothers got killed, the others gained a "level" with increased hd and what now until the final one was a dang behemoth.

hence...its all about how you tell it...

Well, it's just a joke! Best if NOT used!

Sort of, "things we'd LIKE to do as DMs," maybe.

The best way to pump up monsters without cheating or giving wierd powers is to put them in an encounter location that favors their abilities over the PCs. Also, some well-placed traps can really make a difference, and the monster knows where they are so no risk of accidental triggerings by the monster.

Meefman wrote:

The best way to pump up monsters without cheating or giving wierd powers is to put them in an encounter location that favors their abilities over the PCs. Also, some well-placed traps can really make a difference, and the monster knows where they are so no risk of accidental triggerings by the monster.

You are 100% correct, Meefman. Such are the dangers of Kobolds in my campaign. With a little bit of preparation, those little things can harass a high-level party with the bonus of giving away only a small amount of XP.