CharOp
CharOp is the abbreviation commonly used to refer to the Character Optimisation board on Wizards of the Coast's official forums. It is where players of WotC's games, usually Dungeons & Dragons of variable edition, unite in order to try and break the fuck out of the system any way they can. CharOp is responsible for finding most of the exploitable loopholes and badly-thought-through features in D&D, creating character builds such as Pun-Pun, designing infinite feedback loops that make people infinitely good at something, and otherwise stacking bonuses in unexpected ways to break the game utterly. The only purpose of discourse is to make the best character possible; having a given concept actually make sense is mostly irrelevant, so a charop player would gladly use a half-orc wizard or halfing fighter even though it doesn't make sense in the system, if there were any loophole that would allow for it to be effective.
Before we can go any further in discussing CharOp, we need to narrow things down, and provide some motivation.
Optimization in 4e: What is needed?
Before you can optimize, you must first understand the game. Explaining Pun-Pun, for example, necessitates discussing snippets of rules from a dozen or more books, and this is certainly an optimized character for Dungeons and Dragons, where characters must deal with game-bending effects and situations too wild to list here. Thus, the thought processes for optimization depend on the game. This is a factor with what one sees in 4e, where very little can affect characters--you cannot even take away their hand weapons in this game, and even the 'rust monster' of 4e doesn't really destroy magic items (it only does so, literally, if the players want it to do so).
Primarily, the only thing you can do to a character is hit point damage, so an optimal character might be concerned about having hit points. Unfortunately, the RAW ('Rules as Written', the only thing an optimizer can use to make judgements) for monster damage is so pathetically low, the healing so jaw-droppingly high, that this isn't much of a consideration.
Similarly, characters primarily, almost exclusively, defeat monsters by dealing hit point damage. The other two methods, exploiting flaws in saves--broken and recently fixed by WoTC--and abuse of the Intimidate rules--broken and likely fixed at some point by WoTC, are too easily exploited to necessitate any lengthy discussion.
The primary way characters do damage is by hitting. And this leads to our fundamental philosophy of optimization in 4e: +1 to hit is everything. 4e is an extraordinarly narrow game, there's really nothing else that's relevant. All of a character's powers are keyed off scoring hits. If you can't hit, your powers are worthless (again, there is an exception, in the form of the 'pacifist cleric', but let's focus on the other possible characters, some 99.9% of the possiblities).
How bad is it? WoTC created a feat, "Weapon Expertise", that grants, just that, a +1 to hit at low levels (more at high levels, but that's besides the point). This feat, this simple +1 to hit, is so dominatingly powerful that it's considered a 'feat tax', as all characters, even non-optimized ones, MUST take this feat. Many campaigns simply house rule "all characters get weapon expertise for free", because, in fact, all characters must take it at some point, the sooner the better.
One might think +1 matters more at low levels than at high, but, again, 4e uses a treadmill system. A first level character might have +7 to hit, and will attack monsters with a defense of 18 (i.e., they'll have a 50% chance of hitting). A 20th level character might have a +24 to hit, and this might sound better, but the game is designed to keep characters on a treadmill at all times. A 20th level character will fight monsters with a defense of 35, and so still have a 50% chance of hit.
In other words, "+1 to hit" is just as valuable at first level, as it is at any other level. +1 to hit is EVERYTHING 4e has to offer when it comes to optimization.
Another example: the most powerful Epic destiny is considered Demigod. Why? Because it grants a +1 to hit, in the way of a flat bonus to all attributes.
Yet another example: a +5 magic weapon is valued, according to WotC, at 225,000 GP. If bonuses were worth less at high levels, a +6 weapon shouldn't cost much more. Of course, a +6 weapon (i.e., granting an additional +1 to hit) is valued at 1,125,000 GP, a 900,000 GP increase, obviously worth MORE than any other plus, even all other plusses put together.
Even WotC acknowledges: +1 to hit is everything in 4e.
Why must you optimize in 4e?
Now that we've established that "+1 to hit" is everything, now we need the motivation for why optimization is important, and critical in 4e:
4e has been designed with optimization assumed, and nearly all character abilities are based around combat, and combat is balanced around optimal characters. A typical fight with optimized characters, once you get into paragon, can take 2 hours, more if it's even remotely challenging. Using sub-optimal characters double that time, sometimes more, which is why complaints of 'long fights' are so common on the message boards. Such grindy battles are the results of players falling into stupid traps, such as building half-orc wizards or halfling fighters, or picking +2 proficiency weapons instead of +3, or even picking a cool "+1 Lightning Burst" weapon instead of the dull, but critical to the game, "+2 weapon".
Now, 4rries might claim that any race/class combination is viable, but this is pure rubbish. If you pick something that doesn't have the right attribute bonus (that is to say, a +2 to your attack attribute), then you're permanently gimping your character in a way that can never be fixed. Not taking Weapon Expertise at first level, for example, can be fixed by taking at 2nd level. But if you're the wrong race/class combo, it's all over, that character can only be a drag on the rest of the party. So '+1 to hit' needs to be focused on immediately at character generation, and never abandoned as a principle of character building.
So, next time you're caught in a 4 hour long battle in 4e, and the fight is grinding away endlessly, realize this is because someone forgot to grab a +1 to hit.