It does vary by class. Plebes cannot utilize media so therefore cannot have anything (other than issued laptop) that allows for that. So as a plebe- no ipod (though you can have an iphone), speakers (some companies take away issued headphones), video game consoles, dvd's etc. You get all this back youngster year. Plebes also cannot have civvies. This is, of course, for the ac year. Plebe summer is totally different.
Anyone can have recreational sports equipment or instruments as long as it isnt gear adrift (meaning there is somewhere to put it so it isnt on the floor or sitting on a desk). Anyone can have fans.
Firsties can have a mini-fridge. Upperclass can have coffee makers (not sure what year you get this).
No one can have hot pots or microwaves or anything like that. Most companies have microwaves in the wardroom that anyone can use, even plebes. No one's supposed to have candles.