Among the most valuable cards from OS2 are #47a/b Disgustin' Justin & Vile Kyle in my opinion. Part of this is due to the fact that these are checklist backs during an era of GPK where checklists were still being marked. In baseball cards, kids stopped marking checklists by the early '80s. In GPK, it seems that kids stopped marking checklists somewhere around OS3-OS4. Marked checklists from OS1-OS2 are very common. This in itself increases the value of checklist cards. For OS2, checklist cards are #46 and #47.
In addition to being a checklist card, #46 and #47 are also variation cards. If you look on the back of these cards for the name of #49B, you'll notice that it'll say either Schizo Fran or Fran Fran. I haven't noticed much difference between the scarcity of either variation, but collecting both variations can be a little challenging. Not to mention that OS2 also comes in glossy back and matte back variations. I have 3 of the 4 glossy back variations shown here for #47a/b. The matte back variations add one more card each for #47a/b.