Mega Man Battle Network 6, known as Battle Network Rockman EXE 6 (バトルネットワーク ロックマンエグゼ6) in Japan, is a video game developed by Capcom for the Game Boy Advance (GBA) handheld game console. As with the previous three games, the Japanese edition was released in two separate versions: Dennōjū Falzer (電脳獣ファルザー) and Dennōjū Glaga (電脳獣グレイガ). The North American releases are titled Cybeast Falzar and Cybeast Gregar. Later, Japan re-released these games in combo packs with a special colored version of the "Battle Chip Gate", or "Beast Link Gate". This special combo pack was called the Rockman EXE 6 Beast Link Gate DX Edition and contained a special Blue "Netto" version of the Beast Link Gate and one of the games' two versions.
Battle Network 6 marks the end of the Game Boy Advance Battle Network series, as shown in the ending. Keiji Inafune has stated in an interview that EXE6 is indeed the final game in the series. It takes place months after Battle Network 5, and Lan's father has been moved to work in Cyber City, forcing Lan to move there as well. He learns of two ancient and dangerous Net creatures known as Cybeasts as well as the return of WWW who are trying to awaken the beasts. Lan must do whatever it takes to stop them and destroy the Cybeasts before they destroy the Net.
There are many changes in gameplay in Battle Network 6. One of which is the chip-limiting system. It limits how many of the same chips the player can keep in a folder depending on its MB.
Another one is a slight change in the Navi Customizer. Parts can be placed off the map, allowing the player to install more programs, but at the risk of having a bug.
There are Link Navis can be controlled by the player, and have their own special chip, like MegaMan's allies in BN5. However, these Navis can go about the net freely like MegaMan, although their jack-in point is fixed. Link Navi Charged Shots and special chip damage can no longer upgrade themselves. Instead, they are buster-dependent, giving buster-improving chips some more use. Link Navis can also get rid of obstacles that obstruct MegaMan's path, allowing him to reap rewards like mystery data containing rare items, or allowing access to Net Navis with secret information. The Link Navis include Aqua Man in the Falzar version, and Heat Man in the Greger version. The main drawback to playing as another Navi however, is that they cannot use the Navi Customizer.
Another new introduction is the Tag Chip System, which allows players to "tag" 2 chips together as long as the combined MB of the chips is 60 or lower. These chips will appear side by side in the Custom Screen when either one of them is drawn. This system has allowed players to access low-MB chip combos or Program Advances with ease. Chips chosen as tag chips cannot be set as regular chips.
Source: Wikipedia, "Mega Man Battle Network 6", available under the CC-BY-SA License.