Zombie soldier/doc
Always found around military outposts and FEMA camps, but all-too-often as the remnants of a lost patrol or staffing a roadblock. Slightly faster and much tougher than normal zombies, early zombie soldiers should be taken on with care, by leading them into unfavorable terrain. Their armor means early makeshift weapons are much less efficient against them.
Zombie soldiers are known to carry military grade loot (ammunition, firearms, military grade tools/electronics, military grade armor, etc). Early on that can be a fortune, later on they're still a good source of Kevlar plates for crafting and repairs (firefighter gear is often a lower risk source however).