Your accountant said it quite well IMO. If you can sit with the taxman and explain to him in good faith the business purpose of expenses, he will accept them as such.
In many countries--don't know about yours--there is no need to make a direct profit of a specific expense. You could for example buy a Rolls Royce instead of the smallest Japanese car model, but as long as you can prove that the car is only used for business purposes there is no problem.
Your example of a Nintendo DS is a special situation. The taxman knows that this is the type of product which can and will be used often for non-business related activities so he may ask for more proof that it isn't used for private purposes. In that specific situation it would be better to sell it after the review for for example 80% of the price you paid to buy it, than letting it get dusty in a drawer. Selling it would be also better from a business perspective because it would loose its original value in a few years in your drawer.