The 2-8-8-4 Mallet Yellowstones, then it would have to be a S2 4-8-4 Northern, S4 4-6-4 Hudson , 2-6-0 Mogul.
BNIRRLives
Any steamer,but for multi-engined I love the UP 4-8-8-4,C&O 2-6-6-6,NW 2-6-6-4,NP 2-8-8-4 for single engined locos,the CNW 4-6-4's and the streamlined 4-6-2's
C&NW Forever
Alex