When you speak of "Spyderco Knives EVERY Knife collector needs", are you talking about knives that represent Spyerco's core lines (i.e. Delica, Endura, Military, Manix)? Or are you talking about collector's items that are odd, rare, valuable for example?
Spyderco's first knife, the Worker, would be an obvious choice. The C15 Bob Terzuola, Spyderco's first collaboration, first liner lock, first US made knife might be another. Beyond those, it comes down to what and/or why you're collecting knives.
No "must have"s, not collecting entire sets for me. Been there. Bought few "must have"s and sold them. Collected one entire set and had hard time to spend $$ for couple variants. So I am buying only what I like and really happy about it.
"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf"
Stretch, Para2, Manix2, Delica, Caly3/3.5, a Sage and a few more. None of these are really collectible though until discontinued .
I personally wouldn't put the Tenacious in my list. Have thought about buying one many times but can't justify it. Similar products deliver better performance so the $30-60 savings isn't a bother. It's an amazing knife still and I can see why people love it.
Since you are talking about "collector's needs", then the C01 Worker should be high on the list, perferably the early 2 or 3 screw clip with unchamfered SS scales. It's the one that started it all and it's still an outstanding piece of work today.