1-20 Heyyy, I've seen this thing before... +1 to all your saves.
21-70 Sitting in that corner flipping that coin over and over really improves the hand-eye coordination: 2 skill points or just slide up to the next thief-function bracket if you're using 1e.
71 You're an experienced mugger with an eye for detail. For each combat round you spend just watching someone (i.e. you're not doing anything except maybe moving and you are not being attacked yourself) you get +d10 to hit and +d10 to damage or +d10 to any attempt to trip, grab, or otherwise mess with the target when you finally do decide to attack. This only works on targets that are already engaged or that you can sneak attack in the round where you finally act. The ability can only be used once per fight on anyone smart enough to notice what you're doing. Also: only works on things with organs (like, not on oozes). Re-rolling this raises the die to d12 then d20. After that you start getting 2d10 then 2d12 then 2d20 etc.
72 Ok, you're not totally useless in a fight. Add your dex bonus to your attacks in melee combat. Re-rolling this this just adds +1 more. If you have no dex bonus, add +1.
73 So I found this scroll in this old man's house, right? You have learned one magic-user spell. It functions as if cast by a 15th level wizard or your level whichever is higher. Determine the spell randomly (d8 for level). It works once, that's it.
74 Oh, sorry ma'am didn't mean to... You can super-easily trip any basically human-sized creature that is otherwise engaged with someone or something else on a successful roll-under dex d20 roll. This only works once per fight unless the enemy is mindless like zombies or for some reason can't see you pull off this tactic. Re-rolling this result means the trip does damage: d4, then d6, then d8 etc.
75 Eeeny meeny miney....moe... You are real good at stabbing people in places they really wish you hadn't. If you successfully attack a foe with basically understandable anatomy (like: organs and stuff) with a dagger (or bodkin or whatever), you have the option to leave the dagger in--in some horrible place. The dagger will do d6 ongoing damage per round and will do d20 if they take it out. Yes you can just keep doing this to them over and over like they're a pincushion if you buy a lot of daggers. Magical healing will allow safe extraction of the dagger as will decent mundane medical attention. If you re-roll this result the die of damage for the ongoing damage goes up: d8, d10, d12, d20 etc.
76 All that drinking in the Melting Strumpet has finally paid off. You know a secret. One of two kinds of secret, to be precise: either a piece of useful lore about a legendary treasure or magic item that you encounter or an embarrassing fact about an NPC. Mechanically: once per session you may astound your party's condescending wizard by pulling this lore or rumor out of your ass by making a successful roll-under int check. If you fail, screw it, you can't do it this session. Re-rolling this means you try for this twice per session, then 3 times, etc
77 You've been getting steady work in the city and are familiarizing yourself with the tools of the trade. If you garotte someone they automatically lose a turn on a successful hit, if you bola a running target they will fall down, if you whip somebody successfully you will entangle a limb for at least one round (or one round longer than normal depending on the rules) and if you drop caltrops or marbles and someone with legs steps on them they will automatically fall down. Re-rolling this result adds damage to any of these +2, +4, +6 , etc
78 The old smack and nick... On a successful melee hit, you may immediately make a Sleight of Hand attempt to grab an item (other than the target's weapon) off a target. This won't work twice on anyone above zombie-intelligence who sees it. Re-rolling this result means you get a bonus to the sleight roll for each re-roll +1, +2, +3 etc.
79 Ok, you're kind of a ninja. You are capable of great acrobatic feats and dodges and leaps. In combat, this allows you 2 separate move actions at any time and you can attack and break off being attacked with no danger of reprisal once per . So you could go: attack move move or move attack move or move move attack. You may do this once per fight plus one more for every time you re-roll this result. (Note this is slightly stingier than the Ranger version of this ability.)
80 You've been practicing with flower pots on old ladies. You are +(entire charisma score) to hit with any suddenly improvised weapon the first time you strike against any intelligent foe (who the hell knew you were going for the breadbox?) and add your whole charisma score to the damage. This trick only works once per fight. Re-rolling this adds +2, then +3, then +4 to the damage, etc.
81 Score! You have d6 doses of horrible drugs that are bad for you. They work by ingestion or insinuation. Unless the GM has some crazy drug table, I'm going to say victims must save or act as if under a Confusion spell for 4 rounds.
82 You're a pro at conning. Your silver tongue gives you a +2 charisma bonus to lying. If charisma checks don't come up much in your game, just say someone of ordinary intelligence you can talk to will pretty much automatically believe one lie you tell per day. If you re-roll this result it goes +2 more, +4, +6 etc. or extra lies per day.
83 The gods of luck smile upon your worthless thieving hide. You may escape death or another equally awful fate exactly once. You must spend at least a round playing possum to build tension but....surprise, you jumped out of the way just in time! Re-rolling this means you get to do it again.
84 Oooo, skull and crossbones... You can make 1+ int bonus doses of poison given 12 hours in a city or large town and 15 gp of materials. It's good for d4 hours and does d10+int bonus damage ingested or insinuated on a failed save. You also have been dealing with the stuff so much that you get a +2 bonus to save against poison in general. Re-rolling this increases the save by 2 and means you can make another dose per 12 hour period.
85 Yesssss! Finally you've found it--that thing you wanted? The big score? The Jewel of the Throckmarten Throne? The parasite that eats bad karma? The magic knife that slits throats all by itself? The comely sibling of the monstrous vicar? Whatever. It's there. 4 sessions worth of adventure away or less. Tell your GM, who then must place it.
You must have a fair shot at it--like any other reward, but there's no guarantee you will get it. If you don't get it by the fourth session you can keep trying or let it go and roll again on this table. However if you choose to roll again and then you do get the thing somehow anyway, you lose whatever gimmick you rolled. GM think up some clever reason why.
86 Ohhh... your head hurts and why is this countertop marble? It's hard to reconstruct but you are pretty sure you scored 5000 units of the local currency (GP? SP? Kroner?) and spent it all in one night. Here's how it works: you have exactly ten seconds real time to say what you bought. You now have all that stuff, assuming it adds up to less than 5000gp. You do not get xp for this treasure.
87 Being something of a coward has paid off. You are + 4 to hit with a bow or crossbow if you spend a round aiming. Re-roll? +6, +8 etc.
88 Haaaa! It was me all along! You have learned the art of disguise. Mostly. It's a your Int vs. their Wis roll, assuming you have access to about 40 gp worth of stuff or the kind of materials you'd find in a civilized area. Every time you re-roll this you get +2 to the check.
89 You've been working on doing convincing squiggles. You are adept at forgery. Mechanical details work like disguise above: (Int v Wis, 40gp, +2 on a re-roll, etc etc)
90 You've been watching Antiques Roadshow. You can appraise treasure to a nontrivial and nonboring degree: you can estimate the value of nonmagical things flawlessly and if a piece of treasure is not what it seems on any level you will get an inkling. As in, you'll go "Is this not what it seems?" and the GM will go "Yeah, you've seen a lot of jade urns in your day and this is not what it seems somehow--you're not sure how." If a treasure has some unusual or hidden feature of a mechanical or physical nature you will sense that it is there on a successful Int roll. You won't know what it is, but you'll sense that it is there. You also have an extra +1 (in 6) and + int bonus (if any) chance to notice unusual features or traps in rooms if you are familiar with the culture that built the room. If you re-roll this result you are reading now, just roll again.
91 Keeping one step ahead of the law is hard work. +1 Dex to racial max, excess goes to Str or Con.
92 You are the steely-eyed one at the end of the bar. +1 Wis to racial max, excess goes to Int or Cha.
93 You're not as dumb as you look. +1 Int to racial max, excess goes to Wis or Cha. Note: You look no smarter.
94 It's weird, people are beginning to believe you when you talk. +1 Cha. to racial max, excess goes to Wis or Int.
95 The whole stop, drop, roll thing has finally sunk in. +2 to reflex save or whatever saves can plausibly be derived from "jumping out of the way" in your system. If a save normally means you take half damage, you take none.
96 You've developed highly advanced avoidance strategies. If you are attacked in a round that you spend doing nothing but dodging and your attacker misses, s/he or it will not only miss but fuck up and lose his or her next turn (if s/he or it has multiple attacks, s/he will lose a number of attacks equal to your level). This only works once on anything of better than zombie intelligence that sees it happen. If you re-roll this result, you get it twice, then three times, then four, etc.
97 He's a card player, gambler, scoundrel--you'd like him. You have pals all over. You have one contact for each thief level you have (write these pals down when they appear). This ability can be triggered in any civilized area (or uncivilized areas that travelers frequent) and HEY, IT'S YOU!!!. (GM, get rolling some random NPCs.) These will generally be low-level underclass types--thugs, mountebanks and freakshow performers and, though they have information, they will not be adventurer-material (i.e. they won't help you fight things or open trapped doors for the most part). However, if you re-roll this result you may do one of the following things: "upgrade" an existing contact to upper class status (inheritance? big score?) or "upgrade" an existing contact to adventurer status (that is: you've made it look like fun and they want some, too.)
The Thief player must not become star-struck by this glittering cache of combatly options. You get 10 seconds to pick what you're doing once it's your turn.