There are many good airstrips for a challenge in the Pacific if you're after a change of pace. Lord Howe Island is a nice challenge for larger craft given the largest plane to ever have landed there is a C-130 Hercules. There is nice scenery available for the area too which is a lovely place to test newly installed planes.
I personally also enjoy flying in and out of Phillip Island (YPID I believe?) because of its narrow, gravel runways which have the ocean at one end.
I do alot of flying in South America, there are many remote strips located there. I believe around 3/4 of South America proves to be very challenging to both aircraft and pilot.