OPI!!!
That or just the Sally Henson are my favorite brands. They last the longest, and the colors are always fantastic.
I usually get bored and do every nail a different color, or alternate colors. I don't go too crazy with designs, just bright pops of color. That or I do a tie dye color dip when I'm really bored.
Mine right now look like vanilla cupcakes with sprinkles from a Nails Inc polish.
(not my nails, but I didn't get a picture)