I just wanted to point out something about all the people who are using the same argument:
There is a vein of arguments that seem to follow what is basically the same course:
"Items spawn at random places and times, with randomly quality/usefulness of item. Sometimes a very useful item will spawn right next to your opponent, or sometimes a very useful item will spawn when you are in a situation such that you cannot possibly reach it before your opponent, such as when you are recovering from being knocked off the ledge. Therefore, that gives your opponent a completely unfair advantage, because you are expected to overcome insurmountable odds."
This argument might work if we were all playing single rounds with one stock or something. However, this tourney is two stocks each round, and best 3 of 5 rounds. Therefore an important statistical law comes into play.
I would like to remind everyone of the "Law of Averages." (If you are familiar with this concept, you can skip the next two paragraphs.)
The Law of Averages is just a statement of fact about occurrences that happen with a certain probability over multiple trials. It states that, even if you get statistical outliers to occur (statistically improbable situations occur) that swing the balance of something in one direction, over multiple trials there will be other outliers, until eventually the whole reaches the average.
In other words... let's use the example of a coin flip. The odds are 50% for heads and 50% for tails. If I flip a coin and get heads three times in a row, it seems that luck has favored heads. However, this does not mean that heads will be in the lead the whole time. Eventually luck will favor tails. Over multiple trials, luck will even out until both tails and heads are equal.
This same law of averages applies to items in Smash. Everyone whines about the possibility of their opponent getting a good item while they were busying trying to recover back onto the stage. Certainly this is a possibility, and it could swing the match in your opponent's favor. However, truly assesing the situation for what it is is not that simple.
First, you are as likely to get favored with a good item when your opponent is trying to recover as the opposite. Think about it; Each matchup is going to go to at least 3 rounds. That means each player gets to see at least 6 stocks or 9 minutes worth of action (Assuming you don't get blown out of the water; I'm assuming some closeness in skill here). How often do items spawn on medium? I have no concrete information here, so I'm going to guess once every 20 seconds or so. That means you get to see a minimum of 27 item spawns. What do you think the probability is that they all favor your opponent? Probably pretty radically small. The chances of items alone truly deciding the match are not good.
Second, the factor that causes you to miss an item is not always random, which is a crucial oversight in the original argument (the one given at the top of my post, third paragraph). So you are recovering and your opponent gets a good item; why are you recovering? If you find that there many more times where your opponent gets a good item while you are recovering than the other way around, there is some logical explanation for it. No person is ever "unlucky" in that regard due to the law of averages; if there are multiple trials then eventually luck will even out. Maybe your opponents are simply better at keeping you busy with recovering, and are busy recovering less often themselves, which is why they are having "better luck" than you; they are simply getting more opportunites to have good luck than you are.
Really, given the above, I don't know how you can say most of the items on that list are somehow game-breaking.
I could still see there being room for debate over the inclusion of the ray gun and the smash ball, as even marginally good luck (receiving that item once or twice more than your opponent) could decide a match, especially with characters like Falco or Sonic where the smash ball can potentially two-stock and therefore decide an entire match. Still, if you think green shell spawns are what is causing you to lose, you are probably blaming the wrong thing.