Current Roster
EMD GP38
CSX #6638 by Life-Like. Purchased from Model Train Stuff after reading the review of these models at Spookshow. While the newer one is probably better all around, the older GP38 is a good starter locomotive and was on sale during July 2010.
It will need a coupler conversion kit from micro-trains (1128, 1129, or 1130). Also I've had trouble with the power pickups and got inspiration from these instructions on how to improve them.
GE B23-7
Formerly Conrail #1991 and still wearing the livery. A model by Bachmann and also was on sale at MTS in November 2010. Another good road switcher to work on the RWRR.
Potential Candidates
EMD GP40-2
CSX uses a lot of these on the prototype railroad in my area. Atlas has made some with the CSX livery.
EMD GP40P
A passenger train version of the GP40 used by NJ Transit and Metro North in New York on the Port Jervis line.
Photos of a SP EMD GP40P-2 project by Donnell Wells
EMD GP40FH-2
A passenger engine also used by NJ Transit. One can buy a custom shell for the LifeLike F40PH model from Imperial Hobby Productions.
EMD F40PH
This passenger engine was still in use in the 1990's on Amtrak lines through North Carolina. Lifelike made one, probably similar to the GP38 above. Though it has a Phase III livery, it should be able to go with the Streamlined Pullman-Standard 72-foot baggage and coach cars from Amtrak Phase I made by Con-Cor or Bachmann. Also the Corrugated coaches (such as the 72' baggage) might be appropriate too.
GE U23B
Another B-B locomotive that would fit into my concept. Atlas makes one with the light CSX livery.
Thomas
I've considered trying to find a Thomas locomotive with the thought that it might interest the kids. I came across an article on About.com that talked about them. Unfortunately the sets are close to $100, which would be better spent on one of the three locomotives below...
4-4-0 American
Model Power and Bachmann both make one, but I like the look of MP better. Would serve as a railfan excursion train with a passenger car set.
4-6-0 Baldwin Ten-Wheeler
Bachmann2-8-0 Consolidation
BachmannResearch
At first, all the local trains I had seen had been pulled by an EMD GP40-2. So far I've identified the following locomotives: CSX #6024, CSX #6026, CSX #6028, CSX #6029, CSX #6050, and CSX #6051
More recently I've seen a 2 locomotive consist crossing the old rail bridge over the Cape Fear, usually heading into Wilmington. One day I was able to identify the following locomotives:
More recent still, I saw a consist with:
Another local train pulls covered hoppers and tankers to the Martin Marietta quarry in Castle Hayne.
In the spring of 2011 I spotted a unit train of open hoppers coming from the quarry, pulled by Dash 8's, and probably headed back to Hamlet.
August 2011 I saw a local at MP 366 pulled by CSX 8312, a SD40. This one had covered hoppers and tankers, most likely headed for Martin Marietta.
Early February 2012 a unit train with empty hoppers was heading past MP 367 back toward Davis Yard. Two big GE AC4400CW's were pulling, CSX #5224 and CSX #5313.
Mid February 2012 a unit train with hoppers loaded with gravel or sand was pulled past MP 367 by locomotives CSX #8446 (EMD SD40-2) and CSX #252 (GE AC4400CW).
Near the end of March 2012, a couple big locomotives, CSX 63 and CSX 986, were pulling a string of empty hoppers back to Davis Yard.
Find more CSX trains in the RR Picture Archives. Also you can find pictures at railpictures.net such as this one of a CSX coal train near Hamlet, NC, and this one of an Intermodal train near Charlotte (notice the rail bed and the grass around it).
Norfolk Southern also runs trains through NC, though not quite down
to my area. This next one is a great picture of
a GP38-2
in the
rain 
.
This picture
of NS
5129
has a good view of the track-side scenery.
Information on scanning railroad radio traffic, and these are the frequencies used in my area. Also need to think about antennas