Someone said: 30-day ab challenge. I just had to repin this because I've been doing it for only 4 days now (and at only 10 reps instead of 25) and already I'm seeing definition. And I've tried pretty much every Ab workout on Pintrest and haven't seen these kind of results.
Insanity Workout - Do each of these 6 moves for 1 minute without stopping between exercises. After you've completed 1 round, rest for 60 seconds, then go again. Perform the circuit 3 times (20 minutes done!) 2 days in a row. Take a rest day repeat.