I can't think of just five figures. Aside from bridge crew/main characters for all eras (which is a lot of figures in and of itself!), my 'priority wishlist' figures are:
-TOS Lokai and Bele
-TOS Gary Mitchell
-TOS Salt Vampire
-TOS Ruk
-TOS Khan
-TOS Romulan
-TOS Kor the Kingon
-TMP Spacesuit Spock
-TMP Spacesuit Kirk
-STII David Marcus
-STII Savvik
-STIII civilian Kirk
-STIII civilian McCoy
-STIII civilian Sulu
-TNG Borg
-TNG Romulan Tomalok
-DSC Spacesuit Burnham
-DSC Klingon Vok
-DSC Klingon T’Kuvma
I tried to steer clear of most characters that were covered in the 90's toyline, but honorable mention goes to the following:
-TOS Sarek & Amanda
-TOS Trelane
-TOS Horta
-STIII Kruge (and pet)
-STVI Chang
-TNG Sela
-TNG Q
-TNG Lore (Descent)
-TNG Guinan
-ENT Shran
-DS9 Jem Hadar Soldier
-DS9 Weyoun
-DS9 Founder
-DSC Book