The nice thing about showing a vacant home is that, for the most part, what you see is what you get!
Some of the foreclosures and short sales I have viewed included some things you did not want like snakes, syringes, needles and more.
And very often the sellers would "throw them in" to close the deal. That was the market we operated in for about five years. Buyers controlled much of the negotiation.
But the times have changed. Sellers are receiving multiple offers. Prices are rising.
Still some buyers are asking for closing costs to be paid, offering "low ball" prices, asking for the appliances - even if not included.
Some buyers do not feel like they "win" unless they get it all... including the kitchen sink! Of course in the current market these offers rarely end up accepted.
Go ahead, ask for everything including the kitchen sink but remember this... The cleanest offer (price, fewer contingencies, etc) will usually prevail.