Clash Kings (Japanese Only)
What looks like an ordinary racer is a pretty decent race and crash game.
Its best during the random game modes like car bowling and destruction derby modes.
Japanese menus though so good luck finding it.
Devil Survivor
What seemed like a cruddy anime like game at first turned out to be a pretty nice stradegy RPG with a story that kept me interested. Though I found myself grinding in one spot and not moving forward in the plot, but its still fun and has some cool music. Also I fail to realize that its apart of the same series Persona was apart of, so that explains why some monsters seem familar.
Space Bust-A-Move
While it is just Bust-A-Move, the customization options, tons of modes and online play all make this rather great despite the over the top cute factor that burns my eyes out.
Brick Em All
One of the simple series games.
Just a simple arkanoid like game with many unique game modes and multiplayer in almost all of them.
I keep this on my cart just cause I remember it so well and its such a small filesize.
Rittai Picross (Japanese Only)
3D picross.
I show this game to family and friends and they just don't seem to get it.
I'm still rather confused about what sqaures and circles over a number mean exactly but I still find it addicting fun.
Though I think they could have made the numbering system more classic picross style than making an outright new one but it's stilll plain fun.
I'll probably drop it if theres ever a homebrew clone of it though.
Unknown Soldier (Japanese only)
3rd person shooter with a war theme. A world war I think.
Pretty straight forward, shoot hte bad guys gameplay.
I keep it on my cart incase of a sudden need of good ole shoot everything 3D style gameplay.
Also hiding behind knee high walls and peeking around corners is possible.
Bangai O Spirts....
Its a good shooting style game, but I can't recomend it over the Dreamcast version.
I just can't seem to get used to the controls or the fact theres no real story mode.
But I have to mention it.
It stays on my cart indefinitly due to size and being Bangai-O related.
Monster Jam - Urban Assault
Not at all a bad racer.
Monster trucks, some random racing modes and basic crush everything go fast win first gameplay.
Its not a great racer but it was certainly better than expected.
Some songs can be a tad annoying though and I can't help but think the PSP version is ten times better.
But ya, its better than most other Monster Truck games for the DS at least.
Giana Sisters
I agree with the reviews earlier in the thread but I have to say its more of a calm smooth paced platformer with plenty of tricky jumps.
Its not real difficult but its not boring easy like Mario.
I could see family and friends dying right off the bat though. Those one step left before you fall jumps can be a pain but add a nice challenge I think.
Around the end you also get to play the original Giana Sisters levels all revamped a bit which was a nice reward for completing the game.
I could name some more, but thats all I have off the top of my head.