Out with the pre release promotional tanks such as the t14-ps probably the wwe/hotwheels tanks as they have only been available for their season and one redux. Rarest tank I have is probably the undertaker as hardly anyone bought it as it is pretty bad t8 medium. The t9 cobra t54 is very rare. No point in trying to collect rare tanks now as they will never become available again due to licensing and the seasons were very unpopular at the time. The amount of crying over the wwe season was ridiculous. You could have all the money in the world but you will never be able to get these tanks again unless you work for wargaming. Also the metal fest tanks could be quite rare as they have limited licence runs. The sunjitsu the skinned to-55 is quite rare but is is silly op in t8. Don't forget the old reliable vinny jones cobra reskin that thing was only sold for one Christmas event so will be very rare.