My favorite brands are: HOM and Olaf Benz.
HOM: the Plume line is extremely comfortable (but not tactile) so it's great for lounging at home, sleeping and wearing under loose clothing when it's hot. It's very sexy, almost like lingerie for men but with a clean masculine look. The plume strings are probably one of my favorite thongs to wear. Although I enjoyed the Freddy string growing up, I've fallen out of love with the new production as the string back tends to get frayed quite easily. I've also come to prefer synthetic materials over cotton these days for thongs.
Olaf Benz: I simply adore Olaf Benz because the designs are clean, tactile and conservative. Their phantom range is my favorite and I'm wearing the mini string phantom as we speak. The phantom mini string is very tactile, fits everything properly and looks pretty cool. Although pricey, I find the quality to be very good and they keep their shape if you use a laundry bag. If you're ever in Chemnitz Germany, they have an outlet store for Olaf Benz/Manstore where you can get them for much cheaper than any online retail store!
I generally prefer conservative cuts, style sand colors to match with the clothing I'm wearing.