There have been several posts on G+ and the FaceBook group asking for house rules. I'm going to put them here where I can amend them. Because often I don't even know that it's a house rule.
I only discover it's a house rule when I go and try to check the rules for evidence, and then discover that it's something I mis-remembered or made up out of the whole cloth. Plus, I play a mix of original ICONS and The Assembled Edition—not intentionally, and I try to hew closer to the assembled version, but I've been playing a long time, so it happens. When we discover that the rules do or don't allow a certain thing, we might just do it that way from then on, or claim that there's a whiff of GM-ium in the air that allows it.
Advantages and Improvised Anything: Because I'm old...uh, old school...I often just do stuff if it makes sense in the narrative. I could do it with Advantages and stunts, but often I just do it. Now that I've thought about Advantages, I can do it with them, but it would take concerted effort to get me to do it the "right" way. So I probably won't.
Fast attack...with yourself: I allow characters to use Fast Attack to combine attacks with themselves for a +1 to the attack. A character who combines and pushes can have +2.
Improvised weapons: So someone does X damage with a strike...for example, we'll say 4. If the hardness of an object is between X and X-3, I say that it does add +1 to the damage, but is damaged or destroyed. (Actual weapons can be different. A pair of brass knuckles could be defined as Strike 1, but you can claim that they're made to do striking. They're probably good up to Strength 6, because you don't hear about people accidentally deforming their brass knuckles in their fist.)
Stretching with improvised weapons: In the Stretching description, it says that you use the lesser of Prowess or Stretching to hit someone. I pretty much ignore this. I don't want it to be difficult to hit someone with a pole...like I want you to suddenly have an effective Prowess of 1, but you get better if the pole is longer. Ewww. If the Stretching is 1 or 2, I just take one off the Prowess to reflect that it's not something you're used to. (And if it's one of your powers, I assume you've trained.) (If I were more mechanically minded, I'd subtract the Stretching from the Prowess, but I'm not. Minus one is enough for me)
Specialties on Slam and Stun rolls: With me, you can use any applicable Specialty levels on the rolls for Slam or Stun attacks. So if you have, say, Wrestling you can apply that level to escape attempts or to the roll to see if you Stun. But you have to pick one place to apply each level of specialty...so if you have Power (Blast) Expert, one level could be +1 to hitting and one level could be a +1 for slamming.
Temporary Qualities: I don't know if it says this in the rules, but certainly I let my players and characters pick up a quality for a few episodes if necessary. Often they're bad qualities, but not always. I generally don't worry about buying them off...that happens naturally in the narrative...but I suppose you could use the experience system as given.