Your preffered Asymmetrical clipping config

[Vesperado]

Looking to make a few pedals clip more like a tube amp would. Before proceeding further, I was curious to see what guys on the forum find to work best for them;

(a) extra diode
(b) mixed spec diode pair
(c) chain of diodes
(d) chain of mixed spec diodes
(e) neither: opamp driven hard

Also, if there is a specific spec, clue me in!!

[idy]

Single MOSFET, gate tied to drain.
Single MOSFET, gate tied to drain, with diode anode attached to source.

First gives clipping in both directions but asymmetric, second lets the opamp clip in one.

[antonis]

Single 1.8V Zener..