Crypt Stalker
The Necron Crypt Stalker (Sometimes fan named as the Super Tomb Stalker) was a supped up Tomb Spyder-shaped Necron construct on steroids that was unfortunately destroyed during the Medusa V campaign where a Chaos Titan blew it up before it could even be reactivated.
The mere notion that Chaos needed a Titan to blow up a Necron construct fills one with imagination on how large and fucking powerful a Crypt Stalker really is. Many in /tg/ just think of the Crypt Stalker as that mythical and elusive Necron Titan that has been missing all these years while others think of it as a Spyder the size of a Titan. Unless GeeDubs or Forgeworld release a canon model of one with the obvious price of being more expensive than a real used car. We may never know.