An interesting type of run that someone suggested to me is a Route run. You choose a route number, (1,2, etc), and then only catch and use the mons that appear on that route from all generations, so for example, Route 1 Kanto, Johto, or the corresponding Route as some regions don't have Route 1(such as Route 101). You could do this with essentially every route number that has a corresponding route for each region. You could also do the same idea but with the Forests of each gen.