As for battle network, I usually just customize my folder with strongest battle chip available. I never really use any sort of strategy, crush them all with brute force is all I do. And I enjoyed fighting that bug-like virus with aura on them (forgot its name), They're pretty cool.
They're called Scuttlest (Scutz, Scuttle, Scuttler, Scutzer, Scuttlest, etc.) and I think they're adorable. Even if they're a pain in the ass in MMBN3 and you're going through the Secret Area (though the Shadows are arguably more of a pain, considering you NEED Sword Chips to hurt them).
I've played the battle network series quite long ago, and I'm enjoying the Star Force DS games now.
Leo, Dragon, or Pegasus? I've got Leo, my friend's got Pegasus, and I laugh at his pain with Crown Thunder (even IF I have similar woes -- HOLD STILL DAMMIT).
Although one strategy has remained throughout the times I've played all these games: paralysis attribute cards.
Yeah, paralysis is a good thing. However, in MMBN at least, I couldn't help but notice that using Confusion on a Navi will root it in place (hence why Flashman, once you've mastered a GroundStyle, is a laugh and a half -- GrassStage program + boatload of Spice = FUN and PROFIT).
Anybody have a least-favorite Navi to fight? For me, it's either MistMan, KingMan, or BubbleMan. Mist because of his LOLPoison, King because of his Pawnage, and Bubble because he's such a wuss that you need to have less than 10% of your max. HP to have at his Beta form (and his spam doesn't help matters any.