>>715856002For the most simple face wreckage? Terra, Celes, Relm, Mog. Mog can be swapped with Locke or Edgar if you like. It depends on which you value most highly; Mog has snow muffler and moogle charm, Locke has steal and valiant knife shticks, plus can use the lightbringer and ultima weapon if you just want to smash physicals, and Edgar has lightbringer/ultima weapon plus the how autocrossbow/flash can easily clear out trash without spending any resources. (Plus inflicting status weaknesses and full party confusion on enemies for Edgar, but those don't come up too often in practice.)
Gau can be an easy bosskiller if you just want to go pure cheese (it's possible to pick up nightshade without too much hassle), but if you want versatility and/or you haven't learned the specifics of cheesing veldt mechanics he'll involve more effort than "simple facewrecking". Praise Xi.