My all time favourite (for men) is Daniel Hechter - not too widely known. His suit and clothing 'cuts' are superb, and the quality of his clothing is unsurpassed. It does not seem to date at all. therefore it does not go out of fashion. I have suits, shirts, ties, trousers, belts, cuff links, and even aftershaves and 'grooming products' by Daniel hechter. Another designers clothing I buy regularly is Pierre cardin, again because of the style and cut of his designs, the way it does not 'go out of fashion' and for the quality and length of time it lasts.
I dont have any though i used to love Mary Quant and Biba back in the sixties and seventies...but these days I only wear cast offs ( they are very nice cast offs though) I am not into labels at all
I have loads...Its hard to say..may be John Galliano and Carl Lagerfield,their work is life long...they created some of the greatest pieces for the most famous fashion houses,so I have a lot of respect for them.There are some young faces now who are taking over...