Hordes of t 3 and t 4 units. Skaven, bretonians, empire(if you can survive the shooting), basically anything that isn't st 5+. With st 4 units you are taking a little bit of a risk but with a flank you should be fine. With hordes you have to be careful though because they will most likely be steadfast the first round or two of combat so you have to make sure you won't get charged by anything else.