Making a Will is not about wealth it is about making sure that what you want to happen to your estate does happen. It gives you the opportunity to specify such things as who will administer your estate, who will care for your children and who will receive specific items of your property.
From a perusal of the decided cases it would seem that this word covers stock market based investments but not money held in a deposit account.
It might well be that this construction sits quite well with the layman's understanding of the word even if puzzling for the lawyers. Again, try to avoid using it if possible.
You probably change your car from time to time, either through necessity or a desire to keep up with the Joneses. If you wish someone to benefit from your car on your death, the safest thing is to say 'any car which I may own at my death'.
Care needs to be taken though if you own more than one car and the other is used by your spouse or child.
He or she may not appreciate a beneficiary making a claim on it. This could make things a little difficult when writing your will. You will need to be precise as to the car intended to pass.
Perhaps it is best to say, 'my Mercedes registration no. 123 XYZ or any car which I may have purchased in substitution therefore during my lifetime.'
Take care also if you have one vehicle for business use and one for personal use.