Looking at the wiki there’s a list of prior event vehicles and drops. Iirc some BP and drop vehicles returned but here’s what I could find (excluding WTM promo vehicles since I believe they are still around as well as the Po-2).
World war seasons
AMX-50 Surblindé
▀Hawk H-75A-2
USS Phelps
BA-11
M60 AMBT
IL-2 M-82
Twitch drops
Dark Aggressor
Pz IIC
Pz III J1
Sd.Kfz.234/2
BT-7
Chi Ha Kai
M5A1
Strv m/39
P-40E-1
Multi vehicle events and Bps (including WW1 and nuclear thunder)
TB-3M-17-32
XF5F
M8A1 GMC
I-301
M8 LAC (USA)
I-29
PBM-3 “Mariner”
Leningrad
T-34E
IS-7
Tu-95M
B-52H
Kingcobra (ahistorical skin)
Tiger (ahistorical skin)
IAR-81C (DB 605)
FIAT 6616UB
IJN Suzutsuki
▃Spitfire LF Mk IXc (CW)
ELC 901
Mosquito J30
RN Luigi Cadorna
Re.2005 (VDM)
WZ141-1
◘SB-25J
▄M46
▄SB2C-5
He 177 A-3
Murmansk
Sholef
PBM-5A “Mariner”
Amiens
T-44 (FM)
LaGG-3-23
He 51 B-2/H
▄DB-7
TKA-412
Swordfish Mk II
LVT(A)(4)
FJ-4B VMF-232
Sd.Kfz.234/3
▄Martlet Mk IV
USS Flagstaff
Kungstiger
␗P-51C-11-NT
IL-8 (1944)
Le Triomphant
M551(76)
Strikemaster Mk.88
HMS Gay Archer
Breda 90/53
B7A2 (Homare 23)
MC-485
SPz 12-3 LGS
S-701
J26 David
Centurion Mk.2
AMX-50 (TO90/930)
◔Bf 109 F-4
Pr.183 BM-21
BV 155 B-1
Type T-51a
Object 248
HMS Cadiz
F-6C-10-NA
Elefant
LCM(6) Zippo
Churchill Crocodile
A-1H
IJN Kirishima
◡Kfir C.10
T-80UD/BE
M.B.151C.1
Late 298D
USS Newport News
◄Tornado IDS MFG
T-80UM2
▂Type 62
▃LVT(A)(4) (ZIS-2)
Me 262 A-2a
Ki-21-I Hei
Vilkas
Mirage 2000C-S4
USS Mississippi
J9 Early
MiG-25PD
␗H-75M
IJN Tosa
CRV Block 2
BI
▃Merkava Mk.3D
Lübeck
Sd.Kfz.251/10
␗F-100F
Ki-48-II Otsu
IJN Kurama
LOSAT
T-72M2 Moderna
USS Davis
Kfir C.2
IJN Haruna
F4D-1
Leopard 2AV
Zrinyi I
Su-25BM
HMS Renown
CT-CV 105HP
P204(f) KwK 38
Sd.Kfz.234/1
Object 279
SGB Grey Goose
Au-1
AMD.35 (SA35)
Shcherbakov
QN506
A-7K
Jaguar E
SMS Ostfriesland
CCVL
Po-2M
MBK-161 early
H-34 (USA)
Whirlwind P.9
VT1-2
▂Phòng không T-34
P-43A-1
Ki-94-II
Sd.Kfz.234/4
Grant I
F7F-3
KV-220
Fw 189 A-1
SU-76D
XM8
JDS Yūgure (DD-184)
◄F-4F Early
SU-85A
T30
M.B.152C1
Fw 190 C
NC.900
P-40C
AEC Mk II
Ersatz M10
Pbil m/40
F-5A
PT-16/T14 mod.
HMS Mohawk
Tandem MAI
Lorraine 155 Mle.50
T18E2
▂MK-II “Matilda”
Yak-3T
PV-2D
Excelsior
MBR-2-M-34
KV-2 (1940)
Bong’s P-38J-15
Comet I “Iron Duke IV”
MTB-422
Turan II
M64
Su-8
PT-76-57
PT-658
LVT-4/40
Beaufighter Mk I (40-mm)
A6Mc
Sd.Kfz.251/22
USS Detroit
E.B.R. (1963)
Voroshilov
M6A2E1
Toldi IIA
▄P-39Q-25
T55E1
ITP (M-1)
Centurion Mk.5/1
Z25
F2G-1
T-10A
Matilda Hedgehog
ORP Garland
Bf 109 E-7/U2
E-100
P-51A
M24 (TL)
RBT-5
▂T-V
BMD-4
Buccaneer S.1
RN Aviere
VL Myrsky II
Ka-chi
A.C.I
AGS
C. 202D
◊MiG-23MF
IJN Hayanami
MPK Pr.201K
MiG-21PFM
USS Baltimore
Type K-8 No.13
Ro.57 Quadriarma
Class 3 (P)
Ar 196 A-3
C2A1
F11F-1
Maxim Gorky
Ikv 73
Freccia P-493
BT-7A (F-32)
P-59A
IJN Yuudachi
AUBL/74 HVG
Bf 110 C-6
HMS Spey
PT-811
▃Merkava Mk.2B
QF 3.7 Ram
J6K1
Jaguar
I-180S
Ju 388 J
HMS Tiger
MPK Pr.122bis
VFW
MPK Pr.122bis
H.P.12
Saint Chammond
A7V
Mark V
Garford
Beutepanzer IV
Garford-Beute
Solo vehicle events
SMS Baden
PLZ83-130
Jaguar IS
Churchill AVRE Petard
Eremin’s Yak-3(e)
Alcione
Object 292
Boxer MGS
HMS Barham
▄F-14A IRIAF
◢F-5A(G)
Strasbourg
FIROS 6
IAR-93B
FV4030/3
▄HF-24
T-34-85 “Partisan”
Meteor FR.9
T86
Mackensen
Shisaka
F-106A
EFV
R400
T-72B3 “Arena”
AK-225
▄F-6C
Glaive
◘F-16A
USS Oklahoma
Oktyabrskaya Revolutsiya
Spitfire Mk Vb (Float)
Scimitar Mk.2
YouTube cup
Challenger 2
Super Mystere B2
Leopard 2A5
M1A1
T-80U
