I'd start with this as your base sentence:
There were many mottoes on the flyer: "Make love, not war", "Periods sucks, commas rule", and "Save water, drink beer".
Then play with adding the aside. The fact that you have a favorite is of no consequence to the rest of the sentence, so should punctuate it separately.
You have three basic choices for tone: Subtle, Neutral, and Bold.
Subtle
There were many mottoes on the flyer: "Make love, not war", "Periods sucks, commas rule", and (my personal favorite) "Save water, drink beer".
Parentheses scream THIS IS AN ASIDE, but also say, "You don't have to read this." Using them downplays that this is your personal favorite.
Neutral
There were many mottoes on the flyer: "Make love, not war", "Periods sucks, commas rule", and, my personal favorite, "Save water, drink beer".
This is the most common way to separate an aside (where the aside doesn't totally remove itself from the sentence, like this does), and just gives the reader a heads up that, hey, this is cool to know, but not vital.
Bold
There were many mottoes on the flyer: "Make love, not war", "Periods sucks, commas rule", and—my personal favorite—"Save water, drink beer".
This totally removes your thoughts from the main sentence. It makes the reader stop. Pause.
Read your words. Pause again. And then carry on.
TL;DR
Treat "my personal favorite" as an aside and use whatever punctuation you'd like to impart the desired tone. Just how important is it that this is your personal favorite?