It is unusual in two respects. First of all, its simplicity; few flags except the maddeningly confusing and uninteresting tricolors are so unadorned. Second, it is square. Only two sovereign nations have square flags; the other is the Holy See.
You would think that the square, as a more perfect geometrical shape than the rectangle, would be predominant. Nations naturally wish to portray themselves as enduring (sometimes as immutable). The rectangle is not the shape that best portrays that. Note the perfect symmetry of the Swiss flag; rectangular flags lack such perfection.
I have found only one plausible answer to why nations do not use square flags, and even that is just a guess: square flags do not blow as well in the wind. Is this important for purely aesthetic reasons--the majesty of a waving flag--or for symbolic ones as well?
A barren flagpole in itself means nothing; however, a flagpole with a flag waving at the top of it becomes a localized Axis Mundi. Thus, a nation's waving flag asserts its control over the heavens. It lays official claim to the realm of the symbolic (and no nation shall long endure without vesting itself in symbolism, which builds loyalty).
I won't go into the symbolism of the Swiss flag (it should be obvious), but consider that the earliest known precursor to the current flag featured Jesus himself suffering on the cross. It is also worthy of note that although the dimensions of the current cross relative to itself are established by statute, the exact red hue is not so prescribed, so different flags vary.
It is extremely curious that the Swiss allow any variance in this matter. Flags are probably the single most visible symbol of a nation, both at home and abroad, and their symbolism or historical significance usually is very strong. The Swiss flag embodies not only its Christian roots but its origins as a federation of cantons; the flag is the nation's history. But you can fool around with the color a bit. A strange levity to grant; I will discuss it in more detail with regard to the American flag in a future post.
One group fooled around with the color a bit more than usual. The globally known and aptly named Red Cross:
The Red Cross has officially stated (when they refused to recognize the lengthily named Red Star of David as an official Emblem of Red Stuff International) that the flag is not deliberately Christian, but a direct inversion of the Swiss flag.
This seems somewhat controversial. Wouldn't the inversion of a flag's colors imply the inversion of the symbols that flag stands for? And Switzerland stands for peace. Of course, the Red Cross does not concern itself with peace but with war (or rather of helping people who suffer because of it). Likewise, Switzerland is a nation of peace with one of the highest rates of gun ownership in the world. Perhaps then the Red Cross (based in Switzerland) is onto something: the nation sponsors peace with militarization; the organization inverts it by accepting the reality of war and bringing peace into it.
Of course, even though the Red Cross denies that it has Christian roots, it still bears a cross on its flag, adopted from a country which itself bears a cross which in its earliest forms featured a dying Christ emblazoned. Symbolism, even buried and denied, never perishes. If it did, we would not have a Red Crescent (which could be argued to basically invert the flag of the Ottomans). Why not make a Red Star of David as a similar near-inversion of the flag of Israel (which does officially recognize the symbol)?
The Red Cross states that doing so would dilute the internationalism of their symbols, and that is certainly true. Perhaps the protests by certain nations, including Syria, against the Red Star had something to do with it. Why did they protest? Because nations know that symbols have power, and a symbol's meanings, whatever an organization may claim, never lose their original meaning. The Red Cross and the Red Crescent are both implicitly religious symbols and always will be. For that reason alone, the logical third member of the trio cannot join them, despite the very practical and beneficial nature of the organization in question. The sacred trumps the profane as nations fight wars solely over symbolism.
Never think those wars are not important.