> pseudo-device pty

pty(4) - pseudo terminal driver

You almost certainly want this -- without it, telnet and rlogin can't
work.

> 	      tb

tb(4) - line discipline for digitizing devices

Unless you've the relevant hardware, you don't need this.  I've been
removing this device from my kernel for years.

> 	      md

md(4) - memory disk driver

I doubt you need this in a production kernel.  I think some of the
install kernels require it.

> 	      vnd

vnd(4) - vnode disk driver

Sometimes useful.  Building install/boot diskettes uses vnd to build
the disk image in a file.  Probably you don't need it if you're
trying to reduce the kernel size to the minimum.

Regards,

Giles