Obenauf's Leather Preservative is great.
Apple Leather Care Conditioner, a good liquid conditioner.
Lincoln shoe polish. The best.
Melotonian shoe cream. Good when the leather is dry.
Black and light colored shoe brushes.
I have a Mont Blanc Meisterstuck 144 that's twenty + years old. It has a 18c nib and is a great fountain pen. Of course it's well worn in but it's large, comfortable, never leaks and is a design classic (although common nowadays). I also...