The rarest of the rare for me:
1996 U.S. Army version of the wood Sherman (appears on cover of 1996 'Achtung! flyer, never in any price list, less than 5 made);
1996 8th Army version of Austin k2 Ambulance (never appeared in any flyer or price list 5 made);
1996 "Les Miserables" set - commissioned for opening of the musical in Hong Kong, most given out by the producers to VIP's,the few others only sold in Hong Kong via the June, 1996 Hong Kong flyer)
The overall rarest figure set is clearly the matt WS04, followed by the glossy Free French. Some quotes from the book about these sets:
"By the Winter 1992 Dealers Dispatch King & Country had added 2 sets of very primitive glossy 82nd Airborne figures, USP1 and USP2, as well as 2 Glossy Free French sets, FF1 and FF2 and a glossy U.S. MP, MP1. . . .
Sets FF1 (Foreign Legion) and FF2 (French Marines) each consisted of one standing officer, one marching sergeant and a combination of marching riflemen, standing riflemen and a trooper marching with a grease gun. The Free French appear in U.S. Style uniforms with French flags on the shoulder, wearing French style head gear (foreign legion kepis for FF1 and orange sailor cap with red pom-pom for FF2). Andy sculpted two basic bodies for these figures (as well as the U.S. MP), one standing and one marching. He sculpted three different heads (one with Kepi, one with French Marine hat, one with helmet/goggles). He sculpted two basic right arms (one carrying a grease gun, which could be mounted with the gun angled up or down, one carrying a slung rifle) and two basic left arms (one arm akimbo, one hanging down), and combined variations of these bodies, heads and arms to make the different figures. The Free French sets were originally listed in the winter 1992/1993 dealer dispatch, but a variation of the set as marching U.S. figures is depicted in the 1996/1997 Warbirds Flyer. The author only recently obtained set FF1 in November, 2007, and these two sets are certainly the rarest of the glossy WWII figures. According to Andy Neilson, these Free French figures were just not selling, so Andy and Gordon took the remaining castings, replaced the heads with the head from MP1, wearing a helmet with goggles, and sold the remaining sets as U.S. troops. These figures are in an extremely natural and realistic pose, with perfectly proportioned bodies, heads and hands. This level of sculpting would not be matched by K&C until circa 1999/2000, and the painting is also excellent. The two sets originally retailed for $70 each. . . .
The five original Waffen SS sets, as described above were repainted in matt, and renumbered WS01-WS04, and WS06. The only change to the positioning of the figures was to the tank crew, WS04. This set, the rarest of the matt SS sets, is only depicted in the June-July, 1997 flyer, standing alongside the resin and metal Jagdpanther, and is omitted from all the price lists except the February, 1996 list, which indicates the set is being re-designed, but omits the price, and the March, 1998 Dealer’s Price List. The subsequent collectors’ price lists skip from WS03 to WS05. The Tank commander in the fully black uniform now holds binoculars in his right hand at waist level, with a book held extended down in his left hand. The crewman in the completely camouflaged jumpsuit now has both hands on his hips, arms akimbo. One crewman in a gray tunic and camo pants now holds a MP40 Schmeisser sub-machinegun extended down in his left hand, with his right hand on his hip, arm akimbo. The other crewman in a gray tunic and camo pants now holds a pistol extended down in his right hand, and a cigarette in his left hand. In the March, 1998 Dealer’s Price List this set retailed for $77."