How about making one of these?
Or you can fill it with something colorful/shiny that you want to display. A bottle full of marbles is a nice effect, for example.Or fill it with a colored liquid.Or a combination of the two, like the oil-preserved vegetables one sometimes sees in restaurants. No, I don't know how they prepare those.
Good idea! I didn't think of that!
You can cut the bottle with a wet tile saw and make either a candle or a drinking glass. There are many instructables about glass bottle cutting. Also some other instructables teach you how to make lamps and all sort of other things with a bottle. Just take some time to search.