The Klein 6-in-1 long grip is the ONLY tool to have (if you're going to have just one tool!) It's simply the best 6-1 tool out there, and it's available at Home depot in the electrical tool department. They also make a shorter version. Don't get that one. Get the long version not the short one.
The 6-in-1 has two phillips, two flat head, 1/4" nut driver and 5/16" nut driver. It's the perfect tool for installing/removing the post that was identified in the first post.