I like taking all of Anatolia (in 5.4.1) and then snagging Egypt's islands and using them as a gathering point for a massive invasion of the Ptolemaic Empire at Alexandria. It stops the Egyptians from becoming the juggernaught that they usually becomes, frees the Seluecids to expand and if you keep one rebel town between you and the Selucids and ally them they are unlikely to start a war with you, especially through the Armenian mountain passes, which they seem to avoid.