I would echo previous comments about the Circumvesuviana. Awful things, compounded by the timetable (they stop everywhere, no fast services at all).
The Czech / Slovakian wheeliebins as depicted in the picture further up are strange things too. I would also second the vote for CD non-air con double deck stock - and their former east German equivalent in service with DB.
As for RailJets, they are quite smart and swanky, but I always find them a little too stuffy, no matter what the time of year. In second class they suffer from the same problem as the GWR HSTs, in that the seats are ok for a couple of hours, but I wouldn't fancy doing Zurich - Budapest on one. I've done one in First on one occasion and other than it being too stuffy, found the seats to be OK.
Other nasties for me include the DB class 612 DMUs - hot and stuffy again, uncomfortable seats plus intrusive engine noise. They are not unlike our 158s in many ways, although they have considerably more grunt.
I'm also going to throw double deck TGVs into the mix. Not the worst things to travel on, but I find them claustrophobic.
Oh, and anything with rock hard seats which was desgined as an S-Bahn unit but finds itself, through poor specification and the drive to save costs, on long distance semi fast services. DB, I'm looking at you and your class 442 'Hamster' EMUs!
