Here's my list (I'm not doing this in any particular order):
Southern 4501
Southern 630
Tennessee Valley Railroad Museum 2-8-0 #610 (the one that introduced me to steam)
Norfolk & Western #611 and #1218
Pere Marquette #1225 (Both the prototype version and the 'Polar Express' version)
A Norfolk & Western Y6b that looks more prototypical than the one included in Trainz 12
A Southern Ps-4 (Virtual-Motive-Division offers one, but it's payware)
Union Pacific #3985
Union Pacific #844
Southern Pacific #4449
Santa Fe #3751 and Santa Fe #2926
Milwaukee Road #261
Norfolk & Western M Class 4-8-0 #475
Central Pacific 4-4-0 Leviathan
Western Maryland Shay #6
Iowa Interstate's two Ex-China Rail QJ 2-10-2s
Southern 2-8-0 #154
Louisville & Nashville 4-6-2 #152
Southern 4501
Southern 630
Tennessee Valley Railroad Museum 2-8-0 #610 (the one that introduced me to steam)
Norfolk & Western #611 and #1218
Pere Marquette #1225 (Both the prototype version and the 'Polar Express' version)
A Norfolk & Western Y6b that looks more prototypical than the one included in Trainz 12
A Southern Ps-4 (Virtual-Motive-Division offers one, but it's payware)
Union Pacific #3985
Union Pacific #844
Southern Pacific #4449
Santa Fe #3751 and Santa Fe #2926
Milwaukee Road #261
Norfolk & Western M Class 4-8-0 #475
Central Pacific 4-4-0 Leviathan
Western Maryland Shay #6
Iowa Interstate's two Ex-China Rail QJ 2-10-2s
Southern 2-8-0 #154
Louisville & Nashville 4-6-2 #152