So just to kick this forum off, let's list the trains and operators that you've travelled on/with
Operated by East Coast:
BR Class 253/254 London - York
BR Class 91 York - Newcastle, Berwick-Up-Tweed - Edinburgh and Edinburgh - London ('The Flying Scotsman')
Operated by Eurostar:
BR Class 373 London - Brussels
Thalys Series 43000 (PBKA) Brussels - Rotterdam
NS Class 4000/4200 Rotterdam - Utrecht
NS Class 2400/2600 Utrech - Rhenen - Utrecht
NS Class 8600/8700/9400/9500 Utrecht - Nijmegen
DB/NS Class 406 (ICE 3M) Utrecht - Duisburg
DB CityNightLine Hamburg - Zurich
DB Class 403 (ICE 3) Cologne - Frankfurt Airport
SBB-CFF-FFS Class RABe 514. Zurich S-Bahn, Zurich - Luzern
'Wilhelm Tell Express' from Luzern - Flueen (by Boat) and then onto Lugano (by train)
SBB-CFF-FFS/FS Class ETR 610 Lugano - Milan
FS Class ETR 500 Milan - Rome (Trenitalia)
As well as several normal and overnight loco-hauled trains around places.