How about Iran retaliating by speeding up the transition from Dollar to Euro (or other currencies) to sell oil/gas?
Not bad, eh? :)
Iran could do that, I suppose but there may be difficulties with that. Iran does want to sell its oil in world markets and such a move might make it difficult. I don't know the mechanics of oil sale in world market but if it was easy Iran would have done that by now. No?
Increasing activities of pro Irani terrorists in neighboring countries is probably much easier and most effective (from Iran's POV). The war between Iran and Saudi related groups in Afghanistan and Pakistan has been going on for last 30 years, increasing the temperature there seems more likely.