I have a real soft spot for Fexes and have built a few as I've started my Nid army, (and bought a few second hand.)
Now a personal favourite is what I've nicknamed the "Bullfex." Tusks, Scything Talons, bomb it forward and smash stuff. I've experimented with other loadouts including Dakkafexes with either 4 Deathspitters or 4 Devourers, or an "AT Fex" with Heavy Venom Cannon and Crushing Claws.
I've found the Dakkafexes get mostly ignored and don't really shine as star players much. They're decent, but I mostly play against power armour and vehicle-heavy armies, so they just bounce off most stuff. The AT Fex is surprisingly good now with the buff to the HVC as well as Crushing Claws being a little less rubbish now. The Bullfexes are just a solid all-rounder, (that 5 attacks on the Charge on 3s re-rolling 1s is solid.)
What's everyone else's thoughts? How are you equipping your Fexes this edition?