You need to look at what YOUR strengths are then use them to create your bonus.

For example if you have a decent sized list offer a mailing as your bonus.

As Curtis said, it doesn't actually have to even exist on the day you offer it - future webinars or hour long brainstorming sessions are always great bonuses.

I recently generated around 6k worth of sales promoting a product creation product and my bonus was an hour's brainstorming session and a mailing once the customer had built their product.

The key is to make sure the bonus is highly relevant to the main product. If it is, and it's unique, you should do well.

Tony