Poll: Be Surprised or Know Upfront?

Would you rather know that you're getting a free gift with purchase, or be surprised when you open the package?

I have been including freebies in my packages and letting it be a surprise, because I think that surprises are fun. But I wonder if mentioning in my shop announcement and/listings that a free gift is included with every purchase might be a bit of an incentive to buy?

I have been sending out free earrings with jewelry purchases, but for the photos that have been bought I couldn't do earrings (I didn't want them to damage the pic in transit), so I included stickers in one (it was to decorate a kids' room, so the stickers were for the kids) and in the other, a bookmark. I was also thinking of branching out into cell phone charms.

So, which do you prefer? To be surprised, or to know up front?