How about the Seller making the offer first?

My initial thought - the seller already made an offer by putting the home or condo on the market at a given list price.

I like your willingness to think outside the normal or customary styles.  Seller could offer incentives outside of the listing - for example - during an open house - seller will pay [fill in the blank] buyer on offers submitted before [date and time].

Of course buyers can ask for any given considerations in any event - but who knows - offering additional incentives outside of the listing may be the tipping point for a buyer.  

You know, I read about that a few months back and it seemed like a good idea. I haven't tried it yet, but might down the road.

I've done that when representing a reluctant buyer. The sellers thought it was creative and actually gave us a first offer. We couldn't get it together, but they were willing to give it go and we started negotiations. The other agent was actually open to it after an initial comment that their price was the first offer. She then proceeded to present the idea to the sellers, since the price was too high and was about to face a reduction.

It also helped her secure a price reduction, which did lead to the house being sold shortly thereafter.

It's a cool idea.