The rarest are: kedoshim, pinchas, and mikeitz. The exact frequency depends how you calculate are about 10% (less if you calculate based on how often they occur on tge tur’s 247 year cycle, however as meforshim point out this cycle isnt perfect.)
Tazria us closer to 16%. Vayakhel is rare as well, however this haftora is also for second shabbos chanuka so it is not quite as infrequent as would be.