My favourites to play tend to be trio era and characters that aren’t mentioned too much in the books. Slytherins are my downfall but anybody from the Gryffindor Quidditch team or the lesser known members of the DA have always been solid go-to’s.
Others... there’s been a young Narcissa, Andromeda, a charming (male) OC who happened to be a squib,.. there’s been so many over the years.