My absolutely favorite of all time is Reef's Ginger sandal (pictured left in the taupe/white color combo that I own): woven polyester strap that doesn't rub; "eva" outsole which lasts for miles and miles and slowly conforms to your feet; able to go in the water -- and float in the water for a bit when they fall off -- the perfect flip-flop. $19.99; buy them online here.
I also have a pair of Tory Burch flip-flops -- last year's version -- which come in a standard version and a wedge version this year, both in a variety of colors and patterns. The sandals remind me of Havanas; they have the similar gripping power and are made from similar gentle rubber. The standard version is $45 and the wedge is $55. Find all the versions via this link.
To replace the leather Rainbow flip-flops currently in my collection (these) and currently so worn down that I slip and fall when they hit sand, I very recently purchased a pair of Rainbow's hemp flip-flops with rubber soles in the pictured brown with narrow straps and the single layer arch support. I got them at the Rainbow store in Soho for 25% of their regular price of $40 (so, for $30). Find the hemp version here.
Finally, I really like the Simple "Cushee" sandals, but couldn't find them to try them on "in-person" during my latest shopping adventures. The sandals come in seven different color combinations; my favorite is the "rabbit" pictured left. They are made from a hemp upper, a "eva" topsole and midsole, and a combination of rubber an recycled pulp paper bottom. $28; here.