Some of the courses named in this thread, though I'm sure they're absolutely terrific, are, well, just too pricey. If I had a fat wedge of £$£$ burning a hole in my pocket or access to freebee's I'd naturally love to play them all.
In reality, the ones I'd plump for would be Machrihanish Dunes (played in conjunction with Mach' Old and Dunaverty), the Castle at StA, for it's wacky greens, but only then if played in conjunction with some combination of the New/Eden/Jubilee, and a once off cash splash on the travel etc out to play a few rounds at Askernish, as a yee olde special golf experience, probably playing with hickories. The rest? Well to be honest I reckon I'd rather save the cash to spend on playing the likes of Brora and Southerness and lots of the other cracking wee gem courses that lie in between them, plus some special courses like North Berwick and Prestwick.
But if some kind, generous person said to me the magic phrase "free golf" on any of the newies then I reckon I'd plump initially for the likes of Skibo/Carnigie, Castle Stuart, Kingsbarns and Renaissance, plus Covesea!
All the best.