Firefly first and foremost. Same cast and crew, different network.
Angel needed a season 6 but I’m not sure I would have them do the post apocalyptic thing they wanted to do.
Flying Blind if Tea Leoni can still squeeze into the leather miniskirts she used to wear on the show.
Enterprise with Manny Coto in charge, J+G Reeves-Stevens as the writers and Berman and Braga locked up in Gitmo.
Deep Space Nine had a season left of life in it too. Same cast and crew, same fate for B&B as above.
Boston Legal will eventually go off the air so I would like to spend billions now to make sure it never does.
I would also resurrect all those Fox shows that I never bothered getting into so that it would be worthwhile to get into them (including but not limited to Dead Like Me, Futurama, Wonderfalls, etc).