There is a new tier that I found amazing. It is Partially Used. It is a mixture of RU and NU. It is not an official tier yet, but it has a website. It is user made. You just select Pokemon from a list on the website and make your PU team. Play it in OU or NU I believe. I got introduced to this theme and got pretty good at it. So next time you want to battle or try something new, try PU.