HST's are probably the best ever class of set, as in not just an independant locomotive.
They've survived the test of time and however fast technology produces itself, we're yet to find a train that can beat it. Voyager is doing well, but reliability problems are more regular than the HST, there's that awful toilet smell and of course that "trapped inside with a headache" thing. Same goes for the Pendalinos. Adelantes were built to replace but couldn't last and are being sold off for HST's instead. The nation's only operator of nationwide rail operations is ONCE AGAIN using them. They have become the basis for several designs of similar trains around the world, notably in Australia. They are generally extremely reliable.
I'm scared - I don't want the HST to leave. But let's face it, it's been over 30 years and it's gotta go in the next decade, surely. I don't know why we can't continue manufactering these, but they were the best trains.
As for locomotives, either the 47, 66 or 37. 47's are still popular with freight, passenger and leasing companies, and have become a staple diet at heritage railways. They look nice and are fairly quiet for their day. Decent speed, decent reliability.
The 37 was partly based on the design of the first ever British diesel mainline locomotive and was back in the days of steam, and is still growling up and down the country with freight. Reliability is amazing. The only let down would be the slow acceleration and for those who don't like it, the characteristic growl. However, 37's bound to leave our tracks soon.
The 66 is a fairly recent arrival, from Canada. But it's used in several nations, including Canada, where most of the rail are big juicy beasts. Their reliability is like nothing before, I personally think the "ying" is lovely, it's like the Average Joe of all locos, so simple - like a man called John Smith who is a bachelor and 38 years old living in Wolverhampton and working in an office (sorry to be so stereotypical), generally good, punctuale, but little character. Frequent complaints about A/C, heating, space and seating positions by crew, but these workhorses are the succesor of the 37/47 I beleive.