When I first read LOTR, it was a toss-up between Pippin and Frodo...I was emotionally involved with Frodo's story until he tried to leave the Company at Rauros...I got rather mad at him and upset...so when the story picked up again in TTT with Pippin's point of view, the separation became complete. I love Frodo deeply as a character, but Pippin gets my heart thumping...plus he has a mouth on him, which for a teenager, was pretty attractive. Sassin' a wizard! Correcting a Steward! Pulling a face on a child younger than him (big brother games)! I gotta tell ya, its a pity he didnt have a quest of his own to fill.
Pity? Yes it was pity--pity and mercy. . .Whoops, wrong LotR quote! :) Seriously, now that you mention it, Pippin really does define the reader's viewpoint in much of RotK, doesn't he? My favorite part was the part you allude to where he told the little kid he was really a big fearsome wrestler back in his own country--"I am a halfling: hard, bold, and wicked!" :)