Deadicated to my Mark Todd one - although it is getting on a bit now. I really fancy the full neck fleeces that Weatherbeeta do - but that'll have to wait for the sales!
mine have the aerborn alaska rugs (think they still make them!) they hav a detachable neck but it fits on really well with zips & velcro & iv never had one rub. its expensive but well worth it & keeps my oldie very warm!
The warmest rug I have come across is a high not full neck. Its the Rambo Jumbo Wug. Its about 570g but is not bulky and is easy to put on.
I bought one for my oldie but unfortunately she died before she got to wear it. I liked it because although it was incredible warm it wasn't that heavy.
Someone at the yard bought it off me as it was too small for my new girl.
Lots of horses where I work have shires 500g combo stable rugs. They are pretty hideous (purple!) but they fit well, are quck and easy to taek on and off and they're really warm.