Great list of games, Layton is a good choice, very iconic DS series.
With so many unique DS games, everyone will probably have their own faves that you did not mention, but how TWEWY did not get at least a passing mention is baffling! (Maybe you already did a retroactive on it)
It is the most DS-ass DS game ever made, bar none.
Touch screen combat, dual screen combat with plus pad where both screens matter as you pass a light puck, yelling into the mic, using sleep mode to evolve pins, setting up a STREET PASS shop, giant dual screen ultimate attacks with a banging soundtrack and cute tattoo style art.
That would be my pick, but I do vaguely recall you have talked about it before.
Looking forward to Layton discussion!