I've always been a fan of Filson's Oil Finish Wax products. Their unlined Tin Cruiser essentially unchanged since 1914, and chaps are used frequently and they've served steadfastly for many years, a story for another time...
With all of their water repellent goods comes a can of Filson's Oil Finish Wax. You can also order the tins individually, usually around $10 or so. It's meant to be used to refinish the tin cloth as it wears over time and works excellently for that task.
But oh so many other uses. I like it on hard working leather gloves as it preserves, protects, waterproofs and after some use you end up with a mild tacky traction grip that I like the feel of when using mauls or axes and the like. Some of my leather I treat with Montana Pitch Blend, another great product, but the working gloves get the Filson treatment.
I'm also a fan of applying it to hats, certain hats that I'm likely to wear in the rain, while the tin cruiser is keeping my upper body dry, a treated hat is keeping my dome dry and the rain off my eye wear.
With a single can you can usually do several hats and it lasts a long time. I've treated everything from ball caps to Million Mile hats with the stuff to great effect. Recently I took the time to do a boonie hat, the results of which can be seen below and it has worked outstandingly well.
Cheap, easy, and it flat out works!