I'm a traditional player but I've recently become alerted to the possibility that I might like planeswalkers. After coming to grips with my loss of taste, I set out thinking about cards that have synergy with planeswalkers, to assist me in possibly finding a deck to play. Maybe even a full-on planeswalker deck. Maybe there aren't really any, and maybe it's not necessary.

I couldn't think of many, but I have:

Pernicious Deed, Nevinyrral's Disk
Cards like Ensnaring Bridge, Moat, Humility, Peacekeeper
Oath of Nissa