I loved Joe 90 and remember getting the toy attache case that contained his glasses, a gun and some spy stuff. My brothers and I used to turn our climbing frame into all of the Thunderbirds vehicles. I can even just about recall Fireball XL5 with Robert the Robot and that catchy theme song. As an aside it was nice to see Robert turning up recently in Richard Sargent's "Where's WALL-E?" poster.
There are also his live action series like UFO and Space:1999 to consider but I think it's going to have to be one of the supermarionation shows. It's a struggle to choose between Thunderbirds and Captain Scarlet but I'm going to go with the show that sent me a Spectrum membership card (I wish I still had that). And it has my favourite end credits sequence of all time. My favourite Gerry Anderson show is Captain Scarlet and the Mysterons.