Perhaps high voltage diodes. They are actually a stack of lower voltage diodes, so it stands to reason that they will have a higher forward voltage. But there is a lot less equipment that needs high voltage diodes these days.
i wonder why there is no "renez" diode. low voltage zener such as 3.3V is insensibly worst Izt, imagine for low volt PSU input or battery powered application, 20mA just to get a good quiescent regulation is nuts. now say if i have a 6V PSU or battery input in power sensitive application, i just want to drop it to 5V or 3.3V with minimal quiescent current requirement for mcu or logic chip, a good regulation is not important criteria but board space is, i can just use "renez" diode to do the job, if the manufacturer cannot make a specific and precise forward "renez" voltage drop, like zener has (3.3Vr, 5Vr, 10Vr etc, Vr = renez voltage), at least they can make multiple of Vd drop such as 2Vd, 3Vd,5Vd etc in one small footprint, Vd=normal diode drop 0.7V. why? to save board space instead of using 5x diodes in series to get the desired drop, we can just use one renez. before someone ask why not use LDO regulator chip, i say price, instead of using $2-5, or even the modern $20 LDO, i can use $0.02 renez. there are other applications for this, such as bjt or darlington's base voltage biasing where sometime you will see 2-4x diodes in series will be used.