Well it all depends in what time period I'm playing - Early one, each new loco. is usually an improvement over what went before. The one that I'm always happy to see become available is the 2-8-0 Consolidation as I now have something that is acceptable on moderate grades. By the early 1900s, I'm looking forward to the 2-6-0 Camleback, again for grade handling performance. One, probably unsung, loco. that I like is the 2-6-2 Prairie. When it becomes available in 1912, there does not seem the need for it - the Pacific is faster; the Camleback is better on the hills. However the Prairie comes into its own later on, as its running costs compare favourably with later steam locos. The fact that it remains available for over 40 years means that for me these engines are often the last steam locos. to be retired. The 2-8-2 Mikado deserves a mention for combining speed with grade handling, but its high maintenance cost means that it must be carefully monitered to ensure that it remains profitable to run. The GG1 is of course, the best of the lot - it's appearance in 1935 shouts out to me, 'electrify now!'. Its performance is probably too good since I tend not to buy many steam locos. once it has become available, and none of the later steam locos. since they are just too expensive to run. In RT3 the hill climbing ability of this loco. was lessened, probably to give other engines a look in. The GG1 is the only loco. that I struggle to replace, since by the time the first of the class are life expired (mid 1950s), the best available electric loco. is - another GG1. I can't comment about diesels since I don't often play into the modern era and whenever I do, my main lines are usually electrified by this time. I suppose another question that could be asked is: What do you look for when choosing a locomotive? For all round performance, I tend to look for decent grade handling, low maintenance cost, and reliability. Funny that - I use the same criteria when women are concerned!!! :-*