Shape bonuses never talks about the cross needing to be "holy" at all. In the stories I read, I see crosses being used in crossguards and crossroads to affect creatures (in Ars Terms) classed as having Might in legends.
As usual, this thread stopped being useful a long time ago. Everybody is just repeating his arguments from previous posts. Off I go.
Cheers
Xavi
The infernal associations of the "upside-down" cross are indeed rather recent.
I meant to also ask about magnetite.
I think it is a hard stone (aka lodestone), not a gem of any kind, but thought I should check.
Yes, you're remembering the rule pretty well, and it is for items in general, not just talismans. You must have Superior quality item or an Excellent (any bonus) quality item. If you go beyond Superior to Excellent it provides its bonus to the enchantment process, too. The rule is in C&G, not Covenants, though. See the insert on page 70.
Chris
Thank you very much.
On the other hand, in the specific instance of cross-shaped swords: the shape is not an accident, or a matter of the sword's function as a sword. The cross-guard is far larger than it needs to be to be of use as a guard; and if you look at swords from other cultures, none of them sport that distinctive shape, or even such exaggerated guards. Katanas have a small, round guard. Viking swords from before Christianization, Roman swords, Indian swords... none of them have guards anywhere near that large, or with that distinctive shape. The only other swords or dagger with such out-sized guards are designed as sword-breakers (or at least sword-trappers) and medieval swords are just too heavy to break that way, nor is such sword-trapping a part of medieval sword-fighting (that's the shield's job), and anyway the cross is still not the best shape for that.
The cross-guard is, in fact, a very deliberate attempt to make the sword look like a cross. To make the sword a cross.
So, in this very specific instance, I would indeed argue that cross-shaped swords are both cross and swords, by design, and therefore by essential nature.
Crossbow, on the other hand, are not. Their shape is purely a matter of function as crossbow.
So while I tend to agree with the "essential nature" part
(looks like you got cut off in mid-thought - but I understand where you're going, I think...)
Early on I agreed that if an object were being used as something else, then it might, indeed, qualify as having the "essential" aspect of that thing - to repeat myself, why two crossed sticks is different than a crude wooden cross used by someone with the vow of poverty, or why a pious warrior praying before crossed swords holds something different than an impious poser merely appearing to do the same thing, etc etc.
I'm not sure that ~I~, myself, would fully agree that the guard on a sword was intentionally designed to look like a holy cross - altho' some may have been styled that way, the basic engineering behind it is certainly purely utilitarian. But that is certainly the sort of thing that a SG can interpret for themselves and their saga, on a case-by-case basis, which gets us back to the sort of spontaneous creativity that Xavi and others have been promoting, if far more liberally interpreted than I would (and no one is surprised there, either way!) 
(And, to respond to an earlier comment, I don't find refinement or expansion of a discussion "useless" - if someone can't find use for a clarification of an observation or different example of a position, maybe better not to announce that fact to everyone else.)
+1, agree Hound. The cross debate in this topic was darn valuable to me, well after I'd decided my perspective. In fact I initially was totally against the knight sword being used as cross, debated it, and have come around to that concept as ok in certain constrained circumstances (that are in the thread already). It irks me to see dismissive posts without explanation; thankfully they are rare.
No, a normal basket does not have the shape of a cross. So, it would not receive the "cross" shape bonus. However, if you wanted to enchant one of the intersections in the weave (i.e. not the basket itself), then sure if the weave has a cross shape, it is a "cross" and it gets the "cross" bonus.
Agree.
Agree.
Agree.
"4 Lobes" is not the "same shape". Do a google image search for "liver" and "4 leaf clover". They clearly don't have the same shape. It's not a semantic argument about whether you could plausibly use the same words to describe the shape. The argument is that if you physically had the items in front of you, would a four year old say that they had the same shape?
However, it would be totally fine for a magus to, say, carve a "4 leaf clover" out of "liver". Such an object would be eligible to have the shape bonus of "4 leaf clover" and the material bonus for "liver". And having a character doing this (carving a 4 leaf clover out of liver) is cool. It's a good example of the game mechanics inspiring the players. It's the kind of mad thing that a wizard should do!
Similarly, say, a magus wants to make an item that protects the user from invisible demons --- he can find two glass rods and bind them together as a cross. The cross shape bonus (wards against supernatural) and the glass material bonus (invisibility) both apply. We now have a magic item which is a glass cross. A glass cross would also be a cool addition to a saga, and the reason that we have it is because it makes sense under the game mechanics.
You seem to be saying that because two glass rods are not a proper, blessed by a bishop (or whatever), cross this wouldn't work. Making restrictions like this seems to actually make for a much poorer gaming experience.
Edit: The cross would be fine, but that does not mean that your previous examples would now be.
The glass cross was crafted with the intent and purpose to be a symbol for protection from a special substance. That is very different from a magus picking up two sticks and tying them with string to make a cross and seeking the same bonus. This crafted-glass-cross example is explicit and deliberate, and different from the earlier ones (a giant's shield as a boat, cross-hairs) which were far more impromptu and spontaneous. It is not a fair comparison.
If I may remind you?
By the rules, this Glass Cross would have to be of Superior or better quality. So, whatever what you believe, the end result is the same: You'd have needed design, care and consideration in crafting your glass cross for the specific purpose of being a glass cross. Instead of just grabing 2 rods laying on the floor.
Whatever the metaphysics behind it, in practive, by the raw, your 2 visions work in the same way 
(For the record, I'm on richard's side. The platonic form is the shape of a cross, so if you have a cross, you can tap into it)
I would suggest one of the best example pairs in canon supporting The Fixer, Richard Love, etc. is the sword and the dagger. Ultimately, how physically different are some large daggers from some small swords? They're a lot more similar than many daggers are to each other or many swords are to each other. Yet even if they are quite similar they have very different bonuses.
Chris
Richard, you yourself have argued that they don't have to be "the same" - they are precisely as similar as a holy church cross and two crossed swords, or some of the other examples previously suggested.
Meanwhile, my other questions go unaddressed - re the "shape" of a bandage, or a lamp, or a container (or lack thereof).
I will suggest one last time (much to the relief of all, I'm sure! 
) that "cross" is problematic because it means both a specific "thing" and a general geometric "shape", but looking at many other examples in that same list, we see that they are only "specific things" and simply not "shapes" at all (the title given to the list notwithstanding), and none are merely "shapes" and not "things".
(And the reader is invited to perform their own boolean logic from there, and infer what they will from that!)
However, at this point, I'm happy to agree to disagree. Your position is not convincing to me, but it's certainly quite playable, and that's the bottom line for "being right". 