I twigged about 4 months ago, when DS hit 2, why they've got those shelves at nursery for 'transitional objects' - stuff from home to the rest of us! I know that other children attach to one thing, but my DS is similar to yours, and is quite ranging in his tastes.
One day it'll be a teddy, next day it'll be Thomas or Bob or his purse(or whatever favoured item is that day's Chosen Thing) that gets star treatment, but I've found it's definitely easier to work with it than against it.
For instance, it's much easier to suggest that Thomas would love to go to nursery, and wants to see how clever DS is at getting his coat on, than to try to prompt DS out of the house in any rational kind of way.
I never take the Chosen Thing away from DS (it's not worth the hassle) - instead for instance at mealtimes, I say that Thomas wants to sit on the tumble drier and watch, but wants to eat some of the tomato (or whatever DS doesn't like; it hasn't worked at getting DS to eat tomato yet, but hell you'll try anything once!!!).
At bathtime if the Chosen Thing is not waterproof, we point it out ("Thomas doesn't like the water - he'll get broken" ) and again take the 'watching from the sidelines' stance (from the top of the loo cistern). It can be useful, since when DS inevitably doesn't want to come out of the bath, I suggest that Thomas (or whoever) needs a cuddle.
Anyway, just wanted to let you know that you're not alone and your DS is not weird - mine does it too!!!