While the market is dominated by round watches,I always had a sweet spot for square and rectangular watches.
Unfortunately many (most) of these watches are not a good fit for my wrist;some great designs like the Tag Heuer Monaco,JLC Reverso,Hermes CarréH,PP Gondolo or the B&R watches just refuse to sit comfortably or aesthetically pleasing on my wrist.
I nevertheless found a few watches that fulfill all of my needs.

The Bulgari Octo Finissimo is a delight to wear with it's ultrathin case : a real horological highlight inside and outside.

And the Ti case almost weights nothing!

The Cartier Santos is one of my all-time favorite watch designs: the latest grey version ticks all of my boxes and is super comfortable on the wrist.

A very elegant and versatile watch !

The last one may be a surprise to many as we do not discuss very often the brand Rado.
During the last decades they have however created a few remarkable square watch designs (like the Sintra or Ceramica) and have now as a new highlight the "True Square" model line of which my version is a special edition created in common with the Japanese design studio YOY,named "Undigital",and which is stripped down to the bare essential.

Case and bracelet in matte ceramic with great proportions and extremely comfortable on the wrist.
And powered by probably the best "base" movement currently available : the ETA C07.
Thanks for looking,
Gerard