This way it works universally, rather than making it too swingy. (Where it works or it doesn't ever. And this way you can end it with a Save Ends, or how I'll list it in a sec) It's a "weak" status effect. (Which is how it should be imo) and since it's a Status effect, you can simply add it to certain powers that it would make sense for it to be attatched to. Or make new powers based around the Status effect.
I prefer the add it to existing power approach because some powers just flat out suck compared to the ones you have in Martial Power. It's just there as a "little boost".
Disarmed
- You can not attack.
-You can sacrifice a move action to negate this.
Status effects don't give a save ends, powers do that. It doesn't belong there.
This is a weaker status effect then Prone, which is already pretty weak as far as status effects go.
That's kind of the idea is to make it weak. Otherwise it would be too good.
I might make it a basic attack option as well. So understandably I'm quite hesitant to give it much more.
Works for me. Forcing an opponent to choose between losing their Move action, or being able to make an attack is actually a new thing, and ight be a fun addition to combat. Prone has a much stronger forcing - I can imagine situations where characters who are disarmed choose to move normally, and use their standard action for non-attack purposes, saving up coming out of disarmed status for next turn.
Also possible to build a whole slew of feats and powers around this too (although I assume the intent is to allow it as an option in combat):
E.g. "Feat: Gain Combat Advantage against any foe who is disarmed" or "Power - Hit: 1W+Str mod damage and opponent is disarmed" or "Feat: use simple disarm action as a Basic Attack"
. . . disarmed almost becomes "unbalanced" in some re-fluffings.
This way it works universally, rather than making it too swingy. (Where it works or it doesn't ever. And this way you can end it with a Save Ends, or how I'll list it in a sec) It's a "weak" status effect. (Which is how it should be imo) and since it's a Status effect, you can simply add it to certain powers that it would make sense for it to be attatched to. Or make new powers based around the Status effect.
I prefer the add it to existing power approach because some powers just flat out suck compared to the ones you have in Martial Power. It's just there as a "little boost".
Disarmed
- You can not attack.
-You can sacrifice a move action to negate this.
I would prefer:
Disarmed
- You can not make an attack that requires a weapon.
- You yeild combat advanatage.
- End this condition with a minor action: doing so provokes an opportunity attack.
Picking up an item is considered a minor action, after all. It weakens it as a status effect, but makes it a good way to get combat advanatage. A minor action, no-damage, dex vs reflex rogue utility "attack" would make a good addition to the game. Give rangers something simmilar, where they shoot the weapon out of someone's hands.
This is useless against most monsters and about half of the PC's since they don't actually have a weapon...
Then maybe it would be better to call the condition "staggered." You can refluff it as parrying a orc's blade away, brutally smashing a displacer beast's tentacles in a way that throws it off-balanced, or simply just hitting so hard they have to recover from it.
I created a monster (well... a Human Swashbuckler really) who disarmed characters (as an encounter power).
The power was simply...
+X vrs. Reflex; 1[W]+X damage and any item or weapon held in the targets main hand is dropped into a square adjacent to you
After Effect: Slide any adjacent dropped item 3 squares
It was much easier to DM than applying status effects and stuff like that. It also forced the Fighter to retrieve his weapon and move out of position... now all the melee types in my group carry backup weapons... just in case! 
PGC
Then maybe it would be better to call the condition "staggered." You can refluff it as parrying a orc's blade away, brutally smashing a displacer beast's tentacles in a way that throws it off-balanced, or simply just hitting so hard they have to recover from it.
I agree. My brain failed me whan I suggested "unbalanced" :-)
Edit: I just searched for "staggered" in the Compendium and found no results. So no conflicts with existing RAW or fluff on current powers etc too.
I don't think Staggered and suchlike really conveys what you want to accomplish with a disarm.
Would it not simply be easier to call it disarmed, with the effect...
- The target drops any item (or weapon) held in their main hand, place the item in a square adjacent to the attacker
- Items held in two hands are considered to be held in one hand until the start of the targets next turn
- Monsters cannot make attacks using the weapon keyword until the start of their next turn
- Picking up a dropped item is a minor action
That seems pretty straightforward to me. The target is now effectively unarmed, having either dropped their weapon or had their 2-handed weapon rendered inoperable.
Therefore opportunity attacks must be made unarmed... the target also needs to pick the weapon up again (burning a minor action) and perhaps a move towards the weapon (assuming the attacker made them drop the weapon behind the attacker's square).
This also gives a decent advantage to using a 2-handed weapon (i.e. it doesn't get knocked out of your hands altogether), as it is a free action (on your turn as per above). To resume your 2-handed grip.
It also has a use against weapon-using monsters (i.e. it knocks out their opportunity attacks for a round).
Anyone have any thoughts?
PGC
Most monsters don't have weapons, so the bonus would be situational at best and useless at worst.
The problem I see with having "Disarmed" as a status effect is that unless it's left vague enough to be useless, it eliminates the possibility of an iconic swordfighting scene -- that where the hero (or occasionally the villain) disarms his foe with a flourish, sending the weapon flying far out of reach or else into the air so that he can catch it, usually with a snarky remark. If "Disarmed" is a defined game term with a specific meaning, then what I just described can't be called a "disarm", because it wouldn't fit into anything but the most general (and therefore mechanically useless) definition of a "Disarmed" status effect.
By leaving it common language rather than a defined term, it leaves open a variety of possibilities for disarming a foe, from a standard acting available to anyone (similar to Bull Rush or Charge) which just causes the foe to drop the weapon in his own space, to a Daily class power that allows the character to catch the foe's weapon if he has a free hand. I think that's a lot more flavorful than to create a bulleted list of effects for a "Disarmed" status.
Most monsters don't have weapons, so the bonus would be situational at best and useless at worst.
I think that's the motivation behind a status effect that ignores this difference, and allows refluff.
The cinematic flourish to end the fight version can always be referred on reducing a foe to 0 hits.
Having it as an in-game mechanic is encouraging the disarm to occur during the fight, yet not be the end of the combat . . . arranging mechanics for this needs to be balanced with other things already occurring in combat.
Some of the ideas already proposed probably do that quite well - the difficulty is in assessing them. Worries about "disarm spam" can be judged with play testing. Similar abilities in 3.5E which could be turned into one-dimensional exploit builds (the character's optimised schtick is to Trip or Sunder or Disarm), which not only were over-effective, but destroyed the feel of combat when used, are what make some of us nervous I think . . .
Most monsters don't have weapons, so the bonus would be situational at best and useless at worst.
This is the reason I use "disarm" as a monster attack against PCs... it makes for a good control effect if used sparingly.
It also has the potential to produce cascading effects, since (especially by high level) the character is likely to have feats, powers, and so on that key to the weapon, so the math involved is going to become more burdensome.
"Disarmed" as a power or status effect would probably work much more smoothly as an abstract, something along the lines of:
"... until the start of your next turn, the next weapon attack made by the target is treated as if made by an improvised weapon, though the weapon's enhancement bonus still applies to that attack."
Keeping the Enhancement bonus is critical so that you don't end up with scaling problems.
I agree, knowing when to use such an effect against players is key to balancing excitement and novelty with deparation and repetativeness.
I've only used the "disarm" attack once so far and I don't plan to use it often (if at all).
As for players, I can see someone choosing such an exploit for the novelty value, but it will soon be trained out for something more utilitarian... you want all your powers to be effective when that dragon turns up!
I'd just simply treat "Disarmed" as another way of saying the other guy's at 0 hp (he's dead, he's unconscious, or (if he has a weapon/implement/something he needs to hold to be dangerous) he's disarmed).
Then I'd just change the single power Exorcism of Steel (probably in much the way the OP treats it) and be done with it.
...
Besides the Rustmonster, do any of the monsters anywhere have a "disarming effect"?
I expect that we will see more of them as the game progresses. But I can't think of any off the top of my head really. Right now exorcism of steel pretty much grants this status effect. I suspect at least a few more powers in my games will have this effect added to them as well.