Any of you guys patina your carbon steel knife blades or do you try to keep them shiny?

Patina.

I rub mustard on it, put in zip lock out in sun. (Vinegar) you can use straight vinegar or mustard, ketchup. Either one will do.

If I wanted a more aggressive etch as in real dark, I used to use muratic acid. Don't leave it in there! Just dip and wipe till happy then in to the backing soda solution.

You can use stick on letters or decals with what HMK said.

I used to add patina on the knives I didn't mirror polish, now unless it's a Damascus blade I like to blue my high carbon blades. Great in rust prevention and don't have to worry about acid stains from various acidic vegetables you might cut with it.

Just stick the blade in a potato and leave it over night.

I tried the potato and it didnt give me the results i wanted. White vinegar for about an hour did the trick. Not black but fairly even blue.

Just use it...