Plunking rhymes with:
flunking, spelunking, debunking, flunking, junking, spelunking, banking, blanking, blinking, clanking, cranking, debunking, drinking, flanking, flunking, franking, honking, junking, linking, nanking, nonbanking, outflanking, planking, plinking, ranking, reinking, rethinking, shrinking, sinking, spanking, spelunking, stinking, tanking, thanking, thinking, unthinking, winking, yanking
Plunking sounds like:
plainsong, planking, plinking, plunging, pulmazyme's