Just some quick notes about my Lionel O-Gauge stuff as I find them so I don't forget the details.
My "base" is a 'family heirloom' passed down from my Dad, who got it from his dad in 1950.
It was Lionel 5-car Freight set 2159W. Consisted of:
Pennsy GG1 #2330 5-strip "brunswick green" (only offered in 1950)
#3464 - New York Central Boxcar (operating boxcar, road num 159000)
#6462 - New York Central Gondola (road num 6462)
#6456 - Lehigh Valley Hopper (road num 25000)
#3461X - Lionel Operating "lumber car"
#6457 - Lionel Caboose
Also from my Dad, was the Lionel No. 50 Gang Car with "blue" bumpers.
(found online similar set-- the roadnames are a little different: http://www.dakotapaul.com/items/showitem.asp?iid=5997 )
When I was a kid, we added 2 cars to the set:
#9324 - Tootsie Roll tanker car
#9146 - Mogen David wooden tank car. (roadname is MDWX)
As an adult, I have added a number of additional cars.
Amtrak Phase 1:
#6410
#6411
#6412
I don't have, but would like to add to it the other 4 cars in the set (6403, 6404, 6405, 6406) - they would look great behind my GG1
Assorted other cars, used as my "Christmas set" :
Lionel 1989 "seasons greetings" 50' boxcar
Disney "Christmas" caboose
Rail King / MTH Christmas Smoking Tank Car (Holiday Hot Toddy)