I really like the old tapered-thickness rafter squares that you see in Sally Army stores, tip shops etc. for a dollar or two. So much better quality and heft than the rubbish, lightweight ones available now. To renovate and make legible again, a light sand with some wet & dry and a couple of spray coats of urethane lacquer makes them as good as new. Anything made from just about any manufacturer before the great depression is a class above in my opinion.
The only speed squares I buy are the very cheapest, east asian made aluminium ones that you see in disposals stores. That way, there's no need to shed a tear when it gets bent, trodden on, lost or stolen if it only costs a dollar. It should still be within a minute or two of orthogonality, and the effective equal of the hundred dollar poser's specials. Plus the expensive ones still persist with medieval scales rather than SI units.
I find it amusing that many people I know spend quite a bit on squares. Yes, a Mitotoyu, Moore & Wright or other certified square is going to be more accurate. One can spend hundreds on a well-made combination square, only to drop it or have a heavy rafter fall on it. Even more amusing is to see the uninitiated use an extremely crude marking tool such as a carpenter's pencil, texta pen or the like to mark a rather vague cutting line! This may be quite acceptable for bush carpentry, but realistically has absolutely no place in quality first or second fix building. It would be little short of criminal in cabinetmaking too. Nothing less than a fine, single bevelled hand honed marking knife is acceptable here.
Without a doubt however, my absolute favourite square would have to be Nobex's Octo squares, with the 200 & 300mm ones being most useful. A foot long square that fits in a pocket, with the blade folding out of harm's way (plus another 7 frequently used angles too), using positive sprung ball bearing detents to keep it at the required angle. My pet hate? That the lightly etched graduations don't last very long compared to a combi squares' stamped blade. Otherwise, pure Swedish brilliance & lateral thinking to solve an age-old problem: how to have a square big enough to be useful, accurate enough for precision (although not all of them actually are), and clever enough to be folded, protected and pocketable.