I've no doubt there are all sorts of hilariously expensive Swiss potions for this job, but for me it's hard to beat Liberon's pure beeswax paste with natural turpentine, not least because the wonderful aroma of fresh pine resin it endows everything with.
It should be used sparingly, worked-into the leather with a soft cloth, and either left to dry and then buffed to a subtle gloss, or use a hairdryer to melt it rapidly into dry leather and then leave to cool for a matt finish.
Obviously good for almost any leather, wood, even dry, faded bakelite!
NB: the turpentine will liberate some dye from most leathers, so be sure to allow to dry properly before wearing. Same is true of almost any leather treatment.