I think most monks would agree that there's only one interpreter/compiler that unarguably deserves to be included in a list, namely the standard perl binary stewarded by P5P.

Perhaps because I see things thru P6 colored spectacles, I think the nascent v5 is promising. v5 is a Perl 5 interpreter/compiler project led by FROGGS. Architecturally it's a P6 slang ("sub-language") and relies on the NQP compiler toolchain project originally written to support Rakudo P6 but in principle a user doesn't even have to know it involves P6. It's gotten a quick start by stealing from the Perl 5 grammar STD_P5 written (in P6) by Larry Wall.