Ok, no-one has mentioned them yet, so I feel I ought to give them a plug.
I've always been quite partial to the trains on Arrow Hypers. I like the fact that they're longer than most other steel trains, generally holding 6 people per carriage, and I love the lights which they generally have at the front. They convey a sentiment that it both robust and menacing. Also, each train is a little bit different. Examples: