Does anybody know what plant this is? I'd like to make sure the berries aren't poisonous for my cat.
Without disrespect to your answer Sue, I do believe that this is actually a variegated form of Holly (Ilex spp.). Upon closeup of some of the leaves, you will see the telltale leaf spines. Also, Euonymous berries usually, if not always, retain their "wings" and hang in clusters.
Alas, like Euonymous, Holly berries can be toxic to humans and pets: http://www.poison.org/articles/2014-dec/holly-berries