These days I live a pretty car-light life and like to take public transit when traveling as much as practicable.
Here's my list
US & Can:
ATL
MIA (Yes it can be done.)
DCA / IAD / BWI ( Well scratch BWI, since the time I tried it, Metro was having a breakdown and I wasn't able to get to Union Station in time for the train. Had to Lyft instead.)
PHL
JFK / EWR / LGA ( In order of preference for transit usage to Midtown Manhattan )
BOS / PVD
MDW
MSP
DFW / DAL (actually took DART to transfer between the two.)
SLC
SFO / OAK
SEA
YVR
YYZ
YUL
Europe (almost always take public transit to/from European airports.)
LHR / LGW / STN
DUB
MAD
BCN
CDG / ORY
BRU
AMS
DUS
CGN
FRA
HAJ
BER (before that TXL / SXF / THF )
STR
FKB
MUC
PRG
BUD
ZRH
BSL
GVA
MXP
FCO
ATH
Asia:
NRT / HND
HKG
SHA / PVG
BKK / DMK