In nevada a custom plate is cheap, like $10. Here in CA they are $70. I had custom plates on my '68 Pontiac when I was in highschool: DOOM

I remember seeing DANS-CAR or something like that, and thinking that was pretty funny.

with only a dash you could still get RM -RF, or SUDO SU -, or some other geekery.

That aphid one is good, though.