IE and Etruscan.

<i>(But I'm absolutely sympathetic to the idea that Etruscan may have
had
Anatolian/Aegean connections.)</i>

I've seen such things written of by respectable sources. It's all
impossible to prove, of course, but I've read suggestiopns that
Etrusco-Lemnian may in fact be PIE's closest relative (even closer than
Uralic, perhaps).

Until someone like Sassaure or Verner comes along and gives us new,
seminal insights into how sounds change (i.e., some new 'sound laws'),
only conjecture is possible.