Nintendo's Rumble Pak peripheral will be released on American shores on June 30th, packaged with Star Fox 64. More games are expected to use the pack, as third parties have received the specs needed to create compatible titles.
As of today, the games expected to use the Rumble Pak are: Chameleon Twist, Clay Fighter 63 1/3, Nintendo's upcoming Fishing title, Culture Brain's Hiryu No Ken Twin, Multi-Racing Championship, Sonic Wings Assault, Top Gear Rally, Wild Choppers, and Star Fox 64.
Some of the above games will use Nintendo's new policy on "hot swapping." Since the Rumble Pak takes up the N64 controller's memory cartridge slot, game progress cannot be saved unless the manufacturer puts save RAM in the cartridge. To allow Rumble Pak games to be saved onto a memory cart, Nintendo has made it possible for companies to add in a point in the game where players can "swap" the Rumble Pak for a memory cart and vice versa. The safety screen will undoubtedly keep the prices of third-party Rumble Pak games low and still allow players to save progress and scores.
Games that will reportedly use the swap method include Sonic Wings Assault (known as Aerofighters Assault in the US), Multi-Racing Championship and Kemco's Top Gear Rally.