Not so much house rules, but:
Sudden Apparition: Enemies not adjacent to it do not have line of effect to the [minion].
Die Hard: When dropped to 0 hps, the [minion] is stunned until the start of it's next turn, when it must make a save, on a success, it is dazed instead, until the end of it's turn, when it becomes stunned again. The [minion] can be 'finished' by an adjacent enemy as a Standard Action. Unless stabilized with a Heal check,at the end of the encounter or after 5 minutes of mortal agony, the [minion] finally dies.
(OK, that one was more about "the world you're visiting is really kinda awful...")
Mirror Mirror: (Immediate Interrupt) Trigger: [the Boss] is targeted by a ranged or melee attack. The [minion] and the [the boss] trade places and the attack is resolved against [the minion].
Lurk Between Worlds: The [minion] is removed from play until it uses Facehugger.
Facehugger: (Immediate Interrupt) Trigger: an enemy phases or teleports from or to a square within 10 of the one the [minion] last occupied. Attack: +XOMG vs REF. Hit: OUCH damage and blinded (escape ends).
(They were like 29th level, I can't remember the exact numbers, but they didn't miss often).
OK, house rule or two, for allied minions:
When a minion aiding you in a combat encounter dies, it's exp value is deducted from the exp gained for the encounter.
When a minion drops, it's not killed, but removed from the fight. An effect that would let it spend a surge, a Heal check, or non-surge healing can bring it back into the fight. At the end of the encounter, a Heal check will save it's life.
A similar minion trait another DM used went something like: When [the minion] is reduced to 0 hps he is unconscious & making death saves. If you use a healing power on him, he is returned to 1 hp and you decide his actions until the next time he's dropped.
We wasted so much healing on that guy.
