Arilyn
Hero
13th Age has really interesting "4e like" monsters, that are fun and easy to run. They have "nastier specials," optional abilities which the GM can use to up the danger level. Something like this might help, so the GM can run a more straight forward critter, or up the ante with a more complicated and/or dangerous encounter. This can also help keep players on their toes, because they won't initially know exactly which version of the monster they are dealing with.