Ellen has several forearm scars from encounters with Wasteland wildlife before she could get full body armor and quite a few facial scars in various degrees of fading and healing that are due to helmets being in short supply in the Capital Waste. Also several notches in her left ear, a few burn scars from laser weapons, things like that, and a number of really unpleasant abdominal scars from when she was kidnapped by aliens. She's missing her appendix, four molars, both tonsils, several throat lymph nodes and her gall bladder, and for some reason the aliens installed an extra spleen while they were in there. There was also a fairly nasty scar along part of her forehead at one point that was due to a bad encounter in Point Lookout- Dogmeat fatally interrupted the guy with the knife before it could get worse than that- but that was removed at Milliways. The other scars are largely being allowed to fade with time and periodic stimpak use, but are still largely present.

Fawkes was infected with FEV, which has a whole set of stigmata best described as 'being a supermutant' for the majority of survivors. He's probably got other scars that have been picked up since then, but hell if he remembers any of them.

Stacker Pentecost has circuit lines burned into his skin from where he had to pilot Coyote Tango alone after his partner blacked out in the Drift.

Varric's got a broken nose, don't know where from, and probably has other scars he just doesn't talk about unless he's trying to use them to impress the ladies.

I don't recall seeing any scars on Santo when I watched his movies, so unless he's got a facial scar from before he put on the mask, as far as I'm concerned he doesn't have any.

Adrian Shephard is missing his right arm from the elbow down and has a silver, magically made and magically powered prosthesis in its place. I expect he probably has a few other scars here and there, but the arm tends to make the others a ltitle less noticeable.