I always love trying new hair serums but I always seem to go back to Biosilk. This is my go to product when I flat iron my hair. It makes straightening my hair much easier and is supposed to help protect against heat damage. Although I don't feel that it actually strengthens or repairs my hair, it does make it really shiny and soft without weighing it down. As with any oil/serum it will make your look greasy if you put it on your roots.
Essie is one of my favourite nail polish brands. Although a lot of people may disagree I actually love the size of the brush and find them much easier to handle than the larger OPI brushes. I tend to stick with the more opaque creme polishes by Essie. They usually only require 2 coats, have an average drying time and decent durability. Although the sheer colours are pretty, I tend to stay away from them since they require several coats and take a long time to dry (even when using Seche Vite).