I have purchased over 120 "must have" Spydercos but, if I were to put together a top 10 list of currently available models they would include, in no particular order (just as they occur to me):
1) Military G10
2) Police 4
3) Native Chief
4) Endura 4
5) Manix 2
6) Advocate
7) Gayle Bradley 2
8) Autonomy 2
9) Yojimbo 2
10) ParaMilitary 2
This lists reflects my bias/preference for longer blades, flippers and SD knives. So, they may not reflect the OP's or anyone else's preferences but all of them (except for the newly released Native Chief and also fairly new and automatic Autonomy 2) are knives that have been made/sold by Spyderco for many years and are essential to any Spyderco collection. You can't miss buying any of them.