Unlockable Missions:
Do the following steps to unlock bonus missions in which you can unlock new units.

Mission 11 (black boats) - On mission 10, capture the city east of your HQ to reach mission 11. (The black boat level)

Mission 14 (black bombs) - On mission 13, capture the city in the northeast corner to reach mission 14. (The black bomb level)

Mission 17 (Spiral Garden) - Find the map in Mission 16, Snowy Hunters. It's hidden in the southeastern most city, on the small island with the com tower.

Unlockable CO's in War Room:
Once the characters are unlocked you still have to buy them from Hachi, the cost is listed at the end of wach CO's how to unlock.

Hachi Beat Means to an End in Normal Campaign - 2000 points
Nell Beat Means to an End in Normal Campaign - 2000 points
Kindle Beat Means to an End in Normal Campaign - 4000 points
Koal Beat Means to an End in Normal Campaign - 3500 points
Jugger Beat Means to an End in Normal Campaign - 3000 points
Hawke Beat Means to an End in Normal Campaign - 1000 points
Flak Beat Means to an End in Normal Campaign - 1000 points
Adder Beat Means to an End in Normal Campaign - 1000 points
Lash Beat Means to an End in Normal Campaign - 1000 points
Javier Beat Crystal Calamity in Normal Campaign - 600 points
Grimm Beat Crystal Calamity in Normal Campaign - 600 points
Sasha Beat Crystal Calamity in Normal Campaign - 600 points
Von Bolt Complete Hard Campaign once, than you can buy him from Hachi for 5000 points.

Old Version Maps:
By having old versions of advance wars inserted in your DS at the same time as Duel Strike, unlock new buyables at the the Battle Maps Shop!

Hachi's Land Buy for 1 point when Advance Wars 1 is inserted in your DS
Nell's Land Buy for 1 point when Advance Wars 1 is inserted in your DS
Advance Warpaper Buy for 1 point when Advance Wars 1 is inserted in your DS
Strum's Land Map Buy for 1 point when Advance Wars 2 is inserted in your DS
Lash's Land Map Buy for 1 point when Advance Wars 2 is inserted in your DS
Advance Warpaper 2 Buy for 1 point when Advance Wars 2 is inserted in your DS

Unlock Soundroom:
Beat Normal Campaign and buy it from Hachi.

Unlock Alternative Costume:
Get to Level 10 of higher with a CO and buy the CO edit from Hachi, and you will get the alternative costume in the CO edit menu.

Oozium:
Once you beat Crystal Calamity (the one with the big black crystal), you can purchase Oozium from Battle Maps for 1000 credits. You can then have predeployed Ooziums in your design maps.

Character Wallpapers:
When you complete campaign, you will get the wallpapers for the three COs that you used most that campaign. You can then select those wallpapers from the Display menu.

Unlock Gallery:
To unlock the gallery, simply beat normal campaign once, then purchase it from Hachi for 2000 points.

3 Star Forces:
Once you beat Normal Campaign once, you can use three of the 'Star' Forces with any character Rank 1 or higher. The three forces are Eagle Eye (+2 vison), Gear Head (+2 base repair), and Conquerer (+2 Capture).

Champion Survival:
Beat the basic course for money, turn, or time survival mode to unlock the champion course. Purchase from Hachi for 1000 points each.

Money Champion - Beat basic "Money" survival course
Time Champion - Beat basic "Time" survival course
Turn Champion - Beat basic "Turn" survival course

Hard Campaign Force Unlockables:
You must beat hard campaign then head to the CO Select Screen for your reward

Mistwalker - Allows first strike when attacked during Super CO Power
Soul of Hachi - Allows deployment of units from allied cities during Super CO Power

Special Design Map:
In Map Design mode, hold L and R while selecting the mode to produce a special pre-made map, with "Advance Wars" spelled out in the terrain.

Sending Piperunners directly to enemy bases on the Second Front:
When you send a unit from the Main Front to the Second Front, it will appear on the nearest occupiable terrain to your HQ there. Since Piperunners can only move on pipes and bases...

1) You will need a map with bases on both fronts, ideally with no pipes on the second.
2) Place units on all allied bases on the Second Front.
3) Build a Piperunner on the Main Front.
4) Select it, then select the base you built it on and choose "Send" from the menu.
5) The Piperunner will appear on the nearest occupiable terrain to your Second HQ. Since all of your own bases are occupied, and there are no pipes, the Piperunner will be beamed directly to an enemy base.