ChaosAlert1,549,853 Locked 03 May 2014 03 May 2014
Now, this is kind of misleading as you'd think just playing through all four games (Action Skills Test/Shooting Skills Test/CombatZeal/Pengo) would get you this... but that's not the case. You'll need to play each minigame within all modes, minus Pengo which doesn't seem to have any. Most of these games become unlockable as challenges which should give you an idea of what you're missing. I can't confirm if the other minigames count towards this, but I wouldn't count them out.
If there is anything missing as I'm pulling this from memory, let me know and I'll add it.
The list of challenge games which are unlocked (possibly not in order listed) are as follows:
Action Skills Test
Pin Pon (tap the buttons to ring the doorbell)
Run! (use control stick to run)
Beat Down Tons of Guys! (fight enemies on a path with houses)
Beat Down Tons of Guys! 2 (similar concept as above but in dojo style setting)
Shake Off (use control stick to shake off the enemies)
Drum Can (kick the cans, self explanatory)
Bubble (kick the bubbles, once again self explanatory)
Main challenge only:
Whack-a-Mole (self explanatory)
River Crossing (jump across the wooden platforms)
Air Crossing (same as above, jump on blocks and avoid falling)
Star Catcher (collect the stars, avoid dumbbells)
Karate Chop (time your move to break the stone tower)
Shooting Skill Test
Shoot Watch (tap the buttons to power up the mech)
Tank B (shooting game with tanks, drilling machines, planes etc.)
Obtain Red! (red/green/blue hexagons appear and move around)
Space Nice Bomb (collect the B powerup at the start)
Bullet Evasion (pink bullets randomly spawn on the screen)
Building Evasion (control your ship to avoid colliding into buildings)
Tank A (lots of tanks shooting at you)
8bit (wider version of the CombatZeal game)
Space Can (shoot plastic cans into the trash can)
Main challenge only:
Sphere Evasion (similar to Building Evasion)
Boss Survival (giant bug insect in green shield which shoots at you)
Medal Collecting (lots of ribbons with stars on them shoot from both sides of the screen)
Danmaku Evasion (warning symbol appears on screen before a wave of bullet patterns occur)
Earth Rescue (asteroids falling from everywhere)
Meteor Shooting (shoot large pink rocks which cause bullets to appear once destroyed)
Tank Fire! (multiple rows of tanks shoot at you together)
Rocket Rescue (shoot the bombs off the rocket)
CombatZeal has five games which can all be unlocked once they're started individually.
SF
Asteroid
8bit
Power Up
Boss
You'll need to play multiple times to get some of the minigames to appear, and there doesn't seem to be any trigger for some of the non-challenge minigames.