For tree falling it's safety glasses, ear plugs, helmet, chaps, gloves, steel toe boots. Same thing for bucking except the helmet...unless there's still overhead hazards (limbs higher than head height). Splitting with splitter it's safety glasses, ear plugs, gloves and steel toe boots. Splitting with the maul (very rare) is the same as with the splitter except the ear plugs.
A slight thread derail...I tend to wear safety glasses for a lot of jobs around the house I'm working on...anything (chemical or material) that might have the slightest chance of getting at my eyes.
Kevin