I've got so many things I don't even know where to start! There are certain things I always like to have in stock. For wheels Bilt-Hamber Autowheels, its just the best wheel cleaner, if smelly. For plastics, rubber, leather, CarPro PERL, which is also good for the engine bay plastics and tyres. Best Glass treatment, G-Technic G1.
I change shampoo all the time, I haven't found one specific one that's 'best'. Gyeon Bathe+ is one that coats with a ceramic as you wash. It does work, but you need to use it in the cool weather out of the sun, as it can streak. Optimum No Rinse is really handy for a lot of things, its so versatile that I cant even being to list it all here, best Google it.
Another must have is Sonax Brilliant shine detailer. It leave a nice gloss, can be used as a drying agent and its really good value.