Mega Man Battle Network 4 Blue Moon [GBA]

Secret Boss
To get past the gate in Ura Internet area 5, you need all 150 regular chips. Once you get past it, you can fight the secret boss, Forte, and get his chip, Forte Another

Secret Boss SP
After defeating Forte in Ura Internet 5, Forte SP can be randomly encountered in Black Earth 2. He can drop Delta Ray Edge in Blue Moon, and Black Barrier in Red Sun.

Secret Dungeon
There is a large hole surrounded by purple slime on a platform in Ura Internet area 6. In order to approach it, you need the chips "Bug Curse", "Muramasa Blade", "Black Wing", "Element Dark" and "Poison Anubis". Once you get close enough, it will suck you down to the secret dungeon, Black Earth.
-from WhiteDragon Nall

Blue Moon Ray
Talk to Yuuichiro at ANSA before the end of the game and he will give you this chip

Curse of Bug
Defeat either ShademanSP or LasermanSP without destroying the Green Mystery Data to obtain this giga-level chip.

Delta Ray Edge
S-Rank ForteSP, a random encounter in Black Earth 2 to obtain this chip.

Forte Another
Defeat Forte behind the Standard Gate in the Ura-Internet to obtain this chip.

Signal Red
Bought from a Shop in Ura-Internet 4 for a whopping 100 BugFrags