I'm feeling i need to get back in on the action
Steam: I'm going to have to put the NSWGR Z27 class in here, because in it's gloss black paint job it looks absolutely stunning (and better than the Cadburys purple it was in):
Diesel: It has to be 4001 in Royal Train blue and gold:
Electric: The Cityrail V-sets have always appealed to me, particularly in the current stainless steel with blue front, very appealing (on the left):