I loved Snuffy back when only Big Bird ever saw him. But I've heard recently that EVERYONE sees him now and that kinda spoils the fun, IMO.
Grover was brilliant. Who could NOT love Grover?
Oscar, of course, was a monster near and dear to my heart. He served as a bit of a role model to me.
Elmo wasn't around when I was growing up, but he's kinda cute, in a reddish, high-pitched sort of way. I saw him guest on a cooking show once and to this day I can't hear the word "sauté" without picturing Elmo hopping up and down saying "Sauté!!"
Kermit and his Muppetone News broadcasts were also among my favorites.