(This chart is designed to be the kind of thing you can use during actual play--not just while prepping an adventure.)
1-Is a random PC's mom, in disguise.
2-Despises all life, is a secret sociopath, but drinks too much to get very far with it
3-Wants to be a druid very badly, isn't working out so well yet.
4-Wants to help the PCs because s/he's smitten with one of them. Possibly views other PCs as rivals.
5-Has machiavellian scheme of which every single thing that's occurred thus far in the campaign is actually a part. Secret end of scheme is something unimaginably petty.
6-Is actually high-functioning neutral undead.
7-Helpful, frightened, likes fried food.
8-Terrifed of water. 4th-level thief.
9-Fantastic barber. Doesn't know it.
10-Poet. Knows it.
11-Is some totally bizarre thing from a whole other game--like Rifts or Shadowrun or Monopoly or something.
12-Expert: local knowledge on some place the PCs haven't been yet but will probably get to before the end of the campaign. Suspicious but bribe-able.
13-Desperately trying to sell some real estate--tavern, inn, weapons shop. Will accept ominously low price.
14-2nd level fighter. Has terrible, communicable skin condition.
15-Is a professional witchfinder. Probably somebody in the party qualifies as a witch.
16-3rd level fighter and hilarious! If PCs end up in a drunken brawl in which the NPC takes part (on either side), s/he will make quips. Roll Will save to avoid laughing uncontrollably for d4 rounds.
17-Secret pervert. I'll leave the details up to you.
18-Secret prude. Will berate and shun anyone who appears to be having fun.
19-Gambler. A pretty good one actually. If the PCs can get on his/her good side they may catch some run-off from his/her post-winning spending sprees.
20-Scholar. Expert on first subject PCs happen to need information about while in his/her presence. Impatient and easily offended, however.
21-Inordinately fond of the halfling's pipeweed. Annoying. Wears sandals.
22-Inventor. Capable of coming up with mildly anachronistic technology. Sleeps too much.
23-Paranoid lycanthrophobe. Talks to no-one at night. Locks self up on full moons.
24-Has an entirely undeserved reputation as a lout in nearest city. Is actually quite charming.
25-Has an unusually well-maintained collection of dollhouses.
26-Carves chess pieces when nervous. Isn't very good at chess. Plays for money, though.
27-Reformed crazy wizard. (15th level). No longer casts spells. If the truth comes out and the PCs are very, very nice and reassuring, they may be able to persuade him/her to cast a spell, but each spell cast has a 10% chance of pushing him/her over the edge.
28-Is William Shakespeare. Or nearest racial equivalent.
29-Has bizarre fungus colony growing in stomach. Knows it, and sings to it each night before going to bed. If slain, the colony will escape.
30-Has constant, unaccoutable, faux-european accent-drift. German one second, French the next, etc..
31-Proud. Hungry for glory. Inept.
32-Is nicknamed "The Hyena". The reason for this is, thus far, unclear...
33-Radical democrat. Constantly trying to draw PCs into various regicidal schemes.
34-Gourmet cook/chef/baker. Constantly trading or searching for exotic ingredients.
35-Extremely accomodating. Creepily accomodating. Will let the PCs stable their horses in his/her living room. Talks like Dracula. Totally harmless.
36-Ex-court jester. Not that funny. 1st-level wizard.
37-Always wants to help. Is kind of useless, though. Has a really nice magic sword.
38-Carpenter. Claims to be the son of local deity. Isn't.
39-Was possessed once by a greater demon. Doesn't like talking about it. Blames self.
40-Excellent hunter. Can find, kill, skin and gut a bulette in 12 seconds. Dislikes fighting otherwise.
41-Is actually kind of sweet.
42-Boring. Will talk until credibly threatened.
43-Is in with the in-crowd. Knows where to get the good lotus powder, has friends in all the thieves' guilds, all the local dancers owe him/her favors.
44-Fiercely devoted to random local deity. Was fiercely devoted to rival local deity until fairly recently.
45-Totally Metal. Likes axes, mead, and fire.
46-Is exactly like your favorite character from your favorite book only the opposite gender.
47-Unappreciated medieval art genius. Can do perspective and everything.
48-Amateur doctor. Takes a professional interest in any disease.
49-Likes eating eggs. Has terrible asthma.
50-Knows far more languages than anyone else in the campaign. For reasons unknown.
51-Str 18/00. Has lice.
52-Extremely insecure, addictive personality, whatever s/he's doing, s/he wishes s/he were doing something else.
53-Totally self-deluded, thinks s/he's all that and a bag of chips and that the PCs are thoroughly impressed with him/her.
54-Feels no remorse. Has never seen the ocean.
55-Painfully stupid. Good-natured though. Always pretends like s/he knows what the PCs are talking about, but never does.
56-Has fascinating theories about animal and monster behavior and something called "evolutionne threwe natural selectionne".
57-Can't read but likes to pretend s/he can.
58-Is from a far more sophisticated culture far to the (east, south, whatever) and is sort of appalled and disgusted every time something medieval happens.
59-Acts like Sherlock Holmes (d6: 1-3 Basil Rathbone 4-5 Robert Downey, Jr. 6-John Cleese)
60-Depressed, depressing, pessimistic, eerily lucky in all endeavors.
61-Nervous. Knows secret weakness of important monster, but is probably too suspicious to tell anyone.
62-Angry amateur astrologer.
63-Alcoholic idiot-savant thief.
64-Is creeped out by magic. Is trying to grow a beard. If s/he already has one, is trying to decide whether to shave it.
65-Has a personal vendetta against most powerful NPC in campaign. Right-handed.
66-Idealistically committed to racial harmony. Calls humans, elves, dwarves, etc. "demi-orcs". Has a wooden eye.
67-Vomits alot. No reason.
68-Forgetful. Narcoleptic. Handy.
69-A total bureaucratic tool and busybody. Secretly writes down information about everybody s/he's met.
70-Has an obscure ceremonial obligation to do some strange but subtle ritual at dusk every day. May or may not actually prevent genuine dire mystical consequences.
71-Never answers a question directly. If pressed, will cry.
72-Loves his/her job. Jolly and enthusiastic about it. May have Asperger's syndrome.
73-Charisma 18. Terribly charming. Enthusiastic for tales of adventure. Will trade information if the PCs tell him/her what they've been up to.
74-Locked in a Melvillean struggle with some monster/beast a la Bill Murray in Caddyshack.
75-Master spy. Has entirely opposite personality as s/he appears to have.
76-Vegetarian. Fears the sight of blood. Has many foes.
77-Complains about minor physical ailments constantly. If seriously injured, insulted, or aggrieved, will not mention it at all and will go back to complaining about bursitis and toothaches almost immediately.
78-Eminently gullible and convincible--does whatever anyone tells him/her to do.
79-Plays practical jokes. Lives with parents.
80-OCD. Often feels uncontrollable urge to touch dangerous NPCs and monsters on the nose.
81-Knows the languages of animals. Not that they particularly like him/her.
82-Has serious body image issues. Keeps asking if s/he looks good in this?
83-Addicted to opium. Thinks PCs are a whole other group of PCs from a different campaign.
84-Secretly carrying on a torrid love affair with another major NPC in the game.
85-Swears constantly. Good at math.
86-Loves cat more than spouse.
87-Secretly sells familiars on the black market.
88-Ferociously impatient. Interrupts everyone all the time.
89-Common isn't native language--always says "What is the word?...ahhhh..." Likes travelling.
90-Extremely superstitious. Constantly examines omens, signs, and luck charms. Some actually work.
91-Terrible with names. Makes up nicknames for everyone, forgets them, makes up new ones.
92-Has 25 children. Experiments with gunpowder.
93-Has a pet that isn't actually what s/he thinks it is.
94-Never misses a chance to go to the theatre. Is often thrown out for brawling.
95-Will betray anyone who trusts him/her, then confess and beg for mercy. Enjoys beekeeping and horticulture.
96-Has same tattoo as PC. If PCs are un-tattooed, has same father.
97-Has extensive war wounds. Hears things wrong a lot due to ear injury. Hilarity or disaster ensues.
98-Believes that crows despise him/her. Flees from them on sight. Ambidextrous.
99-Acts like Gandalf but is wrong all the time.
100-Amateur shrink--constantly trying to psychoanalyze the PCs whenever they meet. Fears pirates.