I've tried tacky overgrips from Gamma, Wilson, Head, Babolat, and Yonex. Of all the ones I've tried, I liked the Yonex Super Grap the most! My hand doesn't sweat too much, and Super Grap retains its tackiness the best. If you're really looking to stretch the life of an overgrip, you can even use the reverse side, and it will still feel fairly decent!
Another big plus is that Yonex offers the grip in so many different colors, just in case you're looking for a bit of change.