A watch around your fingers clenched in a fist makes for a lovely makeshift (though a wee bit painful) brass knuckle
A tightly rolled up newspaper or magazine makes a sturdy rod capable of shoving a person’s nose up into his brain, this does take some finesse however, so let us skip it.
A broom handle, a bat, some sort of rod made of sturdy material makes for a nice, perhaps one time use bludgeon. A plastic broom handle tends to break but leaves you with a shank of sorts.
Some sort of cord may make a nice garrote, preferably something like piano wire but guitar/cello/violin/etc. will do just fine. Worse comes to worst, something like a mouse cord will suffice in choking the intruder out, if you can hold on long enough. Zip ties work as well, very effectively if I may add, if you can have one long enough to go around the intruder’s throat.
Just about anything and everything in your room can become a weapon. All it takes is a little imagination.