Mike the Headless Chicken lived for eighteen months after being put to the chopping block, living an exciting life on the road with sideshows. Alas, headless Fallout 4 [official site] players are soon to be robbed of their livelihood. The weird and rare bug which let players be dismembered but keep on living is on the hit list for Patch 1.3, which is now in public beta testing for folks who want fixes now, now, now.
On the subject of heads, the patch also fixes companion character MacCready's Killshot perk, which was making players far too good at bursting those little eyeboxes.
Head on over to the changelog and you'll find a huge long list of other tweakes, improvements, fixes. Also on the slate are a few performance and stability improvements, fixes for a fair few quests, new weapon debris effects (which require an Nvidia card, boo), a "status menu for settlers in your settlements", and plenty more. You can read it yourself, I'm sure.
If you want to try the beta now, rather than wait for the patch's proper list, fire up Steam, right click on Fallout 4 and go into its Properties, then the Betas tab, and select the 'Beta Update' option.
But! Dismemberment! Here, watch 'postbroadcast' recount the loss of his own head (also where I snatched that picture up there ↑ from):