Duragloss - 105, 111, 253, AW, 501 and/or 601, 751, 901. Guess you can tell I like most of their products that I've tried. I like the leather conditioner and APC as well but I don't know if they are "must haves." The leather conditioner has a pretty noticeable leather smell if that's what you like.
I will say that I had a bottle of the APC and I wanted to clean my oil drain pan since I stored it immediately after my last oil change and didn't wipe all the oil off the top. It stayed in my storage shed and collected dust on top of the oil and it was pretty filthy. So I sprayed the APC all over the top and as soon as it hit the oil, it dissolved/emulsified the oil. I was impressed.
Optimum -ONR is the only product I've used. It's a must have.