Max turned me onto the Kuhl Wunderer (all nylon button up) ls shirt. Cool, light weight, breathes fairly well, is ventilated, protects against bugs, wicks well, dries fast, and doesn't build up too much stink (since it's nylon vs polyester).
I got mine on sale a little while back, at Moosejaw i believe, for around 40 dollars.
Bought a women's WoolRich 53% nylon 47% tencel button up shirt at STP, and it is now my favorite hot weather shirt, though the fit is not ideal (a wee bit tight in the upper arm/chest area, with a slight flair towards the hips, but otherwise looks like a men's shirt). Super wicking, no odor, dries fast, very light weight, thin, breathable and cool. Unfortunately short sleeved, so i sewed some nylon tulle to the sleeves to add a little bug and sun protection. The top part of the arm is doubled tulle, and bottom is one layer of tulle. It won't provide much UV protection, but a little is better than none. It could catch on stuff though.
I really like the Prana Sutra shirt, 53% Hemp, 44% polyester, and 3% spandex. Originally tried to sell it because the color was too dark (cocoa brown), but i was able to finally lighten it up enough (and decided to keep it). Awesome, somewhat thin, fabric combo for especially hot and humid weather. A bit on the heavy side though at around 11 oz. If it was lighter weight, i would like it as much, and in fit more than, the nylon tencel blend shirt (which weighed around 4.7 oz before i added the nylon tulle sleeves, now weighs 5.3 oz).
Outdoor Research Echo ls shirt with polygiene is pretty good, but can't imagine it's too durable more long term, and can build up odor from non microbial causes (oil buildup).
65% poly 35% cotton thin button up shirts are ok and will work, but in humid weather build up significantly more odor than the above options (but better than 100% non treated polyester shirts).
All the above shirts are best for warmer weather activities, as they are not insulating, especially not when wet. They especially excel in more humid hot weather. All these will be MUCH more durable, and significantly cooler than the Merino, as well as provide more bug protection. With the exception of the poly-cotton shirt, they all have fair to good odor control, but not *excellent*, which Merino does.
Not sure if they even exist, but if you could find a thin 60%-70% nylon to 40%-30% merino intimate blend shirt, it would be pretty to fairly good in most areas if otherwise well constructed/higher quality.