Thinking of replaying one of the Fallouts on here as a Pacifist/Diplomat/Scientist. Anyone finish either one of them without killing, or will I regret not picking any combat skills?

It's possible to finish both Fallout 1 and 2 without attacking enemies in combat or relying on party members to do so. However, some caveats:

1. You will need to cause the death of at least one character in each game through means other than engaging in combat.
2. You will still most likely need to enter combat at times, primarily in the form of random encounters. However, you can always run away.
3. There are several quests you can't complete in a nonviolent run and you obviously can't rely on random encounters/respawning enemies as a recurring source of experience, so there'll be a hard and relatively low limit on the amount of experience you can gain in the game unless you resort to bugs/exploits. It should still be plenty more than you need, though.
4. IIRC, the nonviolent path through FO1 was not something the devs intentionally set out to include in the game so much as a natural consequence of the game's design (non-linearity, multiple solutions to problems, the inclusion of non-combat skills). So it requires a bit of meta-gaming/convoluted actions on your part.

One does not simply will not kill in Fallout 2... ;-)

Too finish the game you must blow up Oil Rig with thousands of humans... :>

Diplomacy and War go hand-in-hand. Death also applies to War.

And War... War Never Changes.

...in any case, no. I'm sure you can only play so far without taking a life in these games. You can minimize, but never truly be a pacifist.

People will die, but you can play the game so you're not the one who actually does the deed. If you convince your enemies they're wrong, they become suicidal and take a lot of other people with them.

And don't forget to try playing with a character with low intelligence! They have special dialogue.

You can create a character with Jinxed, and let them kill each other. This is so fun in New Reno! ^^

I once played a Jinxed character with as many traits and perks as possible geared entirely toward his AC and defenses, and no luck. The result was that he'd often severely injure himself in battle, but not nearly as often as his opponents would simply kill or maim each other.
It was a bit tedious, though.

A colleague of mine recently played F2 with Lk10 and Jinxed. He was a killing machine :D