An old American icon has just met a newer one: starting June 1st, people who buy a Slurpee from 7-Eleven will also have a chance to get an “uber” gift in FarmVille. The convenience store chain has teamed up with Zynga for an extensive campaign that includes several more of its in-store items, as well as the Zynga games Mafia Wars and YoVille.

The partnership marks the latest incursion of social games into retail stores. The most visible, of course, are the ubiquitous virtual currency gift cards that are already sold at 7-Eleven and other chain stores.

This promotion is far more extensive than others we’ve seen, though. In all, there are 21 pairings of real world and virtual goods, plus three uber gifts that players have to buy multiple 7-Eleven products to unlock. Your nearest 7-Eleven may be blanketed with Zynga material; and beyond the store, the partners are even producing video ads featuring MTV stars, and will also advertise in print and radio.

Of course, 7-Eleven is likely to benefit as much as Zynga. With well over 100 million players just between the three promotional games, there should be a steady stream of players coming into 7-Eleven to buy Slurpees — not to mention other, less well-known 7-Eleven products like the store’s branded ice cream.

And Zynga is covering its own bases, in terms of keeping players addicted, by requiring that players complete in-game tasks to get their virtual “gifts”. Some of those gifts will require pretty intensive in-game efforts to acquire, like having to achieve mastery of a new crop in FarmVille to complete the offer.

The promotion will only run until June 15th, so we’ll be able to report back fairly quickly on whether Zynga’s stats receive a bump from the partnership.