Strongest/favorite episode of the set? Hmm, it's hard to pick just one, since there are so many gems on this volume.
But to take a stab at it, I recently watched "Gland of Opportunity" with my family, and we all laughed our heads off. I love the way Duckman instantly switched from slack-off to A-list detective, while still retaining his usual braggadocio. Cornfed's hitting on the lady at the morgue to get in was hilarious (after his poetic pouring-on, he wins her over by saying, "What if I told you had a great rack?", then whips off his fedora to reveal an Afro and further impresses her by juggling chainsaws, priceless).
"Not-So Easy Riders" is another favorite of mine. It wins right at the first scene of Duckman (literally) chasing the almighty dollar, then goes into references to hippie culture, Easy Rider, Five Easy Pieces and Indecent Proposal, all in the span of 23 minutes. Add to that a hilarious vocal cameo by Bobcat Golthwait as a sarcastic Native American. To name just one good exchange in this episode:
Duckman: Did I ever tell you what my dad's last words to me were?
Cornfed: Yeah. "Careful, son. I don't think the safety's on."
Duckman was simply one of the best written shows of our time, IMO.