If you're going to a deserted island and can only take pellets & 2 Crosmans....

[chinaboy]

This post is hilarious. 

But I would think to bring a pumper because you would run out of CO2 eventually. 

[Colt25]

My custom 1322, with CPHP pellets.
And a Benji marauder if I had a pump.

[Plekto]

Assuming you had a source of oil to lubricate the guns, obviously a pumper of some sort.  And a pistol version of the same since there are times when a rifle isn't convenient to carry.

But that's assuming I had to chose only a Crosman.  Truth to be told, I'd chose the following if all brands were allowed:
1 - A HW 95 in .25.  With a synthetic stock added.  No scope - keep the iron sights.  You want a functional and extremely accurate rifle that can work for years with little or no maintenance.  You want to be able to hunt medium sized game like pigs and small deer.  A second choice here would possibly be the FX Independence.  HPA with a built-in-pump is an amazing idea.

2 - For small game, a HB pistol.  There are better guns out there (HW45 as an example), but a desert means dirt and grime, and those old all wood and steel (U.S. made) Crosmans were as close to run-it-over-and-it-still-works as it got.