An interesting trick was opened up to the Rogue with the introduction of Essentials. Because sneak attack was revised to once per turn, rather than once per round, a Rogue who had one of the dreaded minor action attack powers (I'll talk about those later) could use Sneak Attack on his turn, and then ready an action-probably waiting for an ally to attack (Since readying for an enemy's action means they can negate your Ready an Action by not triggering it). Because the Immediate Reaction occurs on another character's turn, you can benefit from Sneak Attack twice per round. Before accounting for Lazy Warlords (yeah, we'll talk about that later too).
I once presented the question "Is there a name for this tactic?" dubbing it Turn Shenanigans. Indeed there was.
"A bad idea." After all, for all the benefits of getting around 1/turn restrictions, when you open up the door to using Readying an Action in order to affect how "turn" effects relate, you can have monsters attacking PCs on their own turns; suddenly, the fighter can't use Combat Challenge because you can't use immediate actions on your own turn!
The conventional wisdom is to just have a gentleman's agreement against this kind of tactic but honestly, when has "Everyone agrees that it's broken so don't use it" been a proper excuse for broken gameplay in the first place?
Before isolating the "proposed solution," I would like to identify something that I do not inherently consider a problem that is along the same vein of thought: delaying one's turn until after that of an enemy who has a status effect that will then expire. For instance, the Wizard immobilizes the enemy until the end of the wizard's next turn. The enemy, who originally acted immediately before the Wizard, now acts after the wizard. Because the status effect is relevant to the Wizard's turn, not the target's, the target can delay in order to negate the effect as it pertains to his own turn. It's unclear if this would work with Daze, and Domination and Stun obviously prevent this tactic. Now, many of you are probably crying foul-
-but I don't see it that way. In order for this tactic to work, the monster necessarily has to be granting the Wizard an additional turn relative to the target's turn. If the wizard and the monster were the only two creatures in the encounter, delaying until after the Wizard is nearly identical to simply abandoning his turn!
On the other hand, delaying your turn when you are suffering from a Save Ends effect prevents you from making that saving throw until the actual end of your turn-but, likewise, it prevents you from having to make that saving throw. This means that if you're one step away from being petrified by a "Second Failed Save" effect, you can wait for your best buddies to apply some pluses to saving throws. Technically, the Delay rules don't state what happens if you lose your turn due to delaying too long as it pertains to saving throws. Conventional wisdom would suggest that at the start of your next turn, you basically resolve the end of your previous turn.
This Save Ends Turn Shenanigans is a significant gameplay decision, but I'm not convinced that it's broken in and of itself. Rather, it just suggests that perhaps Save Ends effects should be increased in danger when it pertains to failing saving throws, because characters do in fact have options to negate their failed saves. Of course, once a creature has been stunned, that's the end of it.
But let's get back to the basic problem of Turn Shenanigans-readying an action. The problem arises because it means that actions originally not intended to take place on anyone else turn end up occurring on their turn. Thus, the solution is simple: with the exception of "You cannot take an Immediate Action on your own" clause, for the duration of the readied action, it is considered the readier's turn, and not the turn of anyone else. Thus, you can utilize Immediate Actions if an enemy readies an action to attack you on your turn, but you may only use said Immediate Action in the course of the enemy's action. The same goes for Opportunity Attacks.
The reason this is the solution is that the purpose of Readying an Action is not to get around the fact that your own actions occur on your turn, but rather to take part of your turn at a later point in time; that is, the Immediate Action is merely a mechanism to accomplish this task. Though it is admittedly somewhat inelegant to put such an ad-hoc solution to the problem that flies in the face of the definition of a creature's "Turn" as being a single connected period of in-game time, it's also important to realize that rounds and turns are abstractions to begin with.