Fallout 1 & 2

How will you be able to beat the boss in Fallout 2 if you're being pacifistic. I haven't tried yet, but I estimate it's pretty difficult to just rely on your companions to beat the final boss.

A lot of guides say you should only put 6 points into Strength, since Power Armor is going to boost it up to 10 anyway. Still until you get the Power Armor, it's pretty hard to get by with just 6 points of strength, especially if you focus on melee attacks. Melee attacks can be devastating if you know what you are doing and are important in the early stages of the game. You sure want to save up ammunition and money for them. I even found them to be somewhat useful later on. If you can do 4 or 5 times critical hit with Super Slegde Hammer, no one is going to mess with you.

I haven't tried it but apparently putting 10 points on luck will give you "unforeseen" positive events. You also get some critical hit bonus and such later one with it. I should try to put 10 points on that elusive attribute some time. The guides recommend this.

Jam it back in, in the dark.

I have actually relied on First Aid a great deal in the beginning of the game, but it's more of a supportive skill rather than anything decisive. If you run out of other healing methods and you are pretty low on health, it could save your life in some critical moments. Later on Doctor skill is much better, but I still liked to use First Aid. Sitting out a few days to regenerate was something I simply had to do a few times. Also you can use it to heal some minor wounds for your companions.

Science is only useful later on when you are supposed to use this skill to handle some computers. It also has some various good effects but I don't remember anymore. In any case, it's not a worthless skill, albeit not specific.

Even Sneak is not useless. I maxed it too 100 very early (80 is already enough), and could sneak my way into almost anything. It was also good to sneak up on people and turn on combat mode, you had a considerable advantage due to more actions points and the initiative.

The best skill is Steal though. Beside stealing stuff you could use this skill to level up like mad. Just encounter some defenseless homeless people, use steal/give back 3-4 times to rack up insane experience points.

There's nowhere I can't reach.

Indeed he sounds more interesting than he really is. Here are his/her stats, which I took from a guide, depending on your level:
9-14: 50 HP, leather armour.
15-18: 70 HP, combat leather jacket.
19-22: 90 HP, metal armour mk II.
23-26: 110 HP, combat armour mk II.
27-99: 130 HP, power armour.

9-13: Hunting Rifle, FN FAL.
14-19: Assault Rifle, Combat Shotgun.
20-26: Laser Rifle, H&K CAWS.
27-99: H&K G11.
The chance for this stranger to appear is (30 + 2*Luck)%. Just get a reliable companion instead I guess, but it's fun to try him/her out.
Apparently you can beat Fallout 2 in 30 minutes... but I mean, these guides are just crazy and possibly spoil all the fun, when you haven't played the game before.
I am toying with the idea of creating a pure dogder. You can easily reach Armor Class >70 with it, so basically you just avoid most of the attacks before any damage reduction modifier comes into play.

This thing is sticky, and I don't like it. I don't appreciate it.