I wrote about this yesterday and wanted to start showing what I was talking about as soon as possible. So here is my second take (after the goblins) on monster advancement tables: Zombies. Have fun!
2 Pimped: Somebody tinkered with the zombies. Stitches, strange fluids, you name it. Roll again and see what was done to them. This is now part of a zombie masters* m. o. and my be encountered again (if he isn't caught).
3 BRAINS!!: They go for the brain. Every successful attack starts (in addition to damage dealt) with holding the victim (STR resolves), 2 successful and unresolved attacks mean the victim is grappled and the next attack is going for the head. A successful attack now also needs a successful save vs. death (-1, -2, etc.) or the victim looses consciousness for 1d4 (1d4+1, 1d6, etc.) rounds.
4 Infectious: Once bitten by a zombie, a character gets a save vs death +4 (+3, +2, +1, etc.). Failure means he'll turn into a zombie in 1d6 (1d4, 2, etc.) days. CON declines in that time to zero. Alter one aspect every time this comes up.
5 Groping: One attack more per round, up to three attacks. After that a DEX (additional -1 every time this comes up) check is needed to keep balance because of the wild attacks. Two attacks do each 1d4 damage, three attacks each 1d3. Upgrade either DEX penalty, number of attacks or damage of one attack.
6 Turn off: One category harder to turn every time this comes up.
7 Faster: They don't lose initiative automatically when this comes up the first time. After that they get faster every time.
8 Wailing: They wail a lot and summon 1 (2, 3, 4, etc.) Zombie(s) more every 3 rounds. (Wandering Monster checks, too).
9 Goo spitting: When hit, spits body fluids at facing enemy. 1 load (+ one more load for every time this is rolled) for 1d4 (1d4+1, 1d6,, etc.) damage.
10 Meaty: More flesh to hit! +3 to hit points for every roll. Getting this for a second time is upgrading the zombie by one more hd, Four times equals two extra hd and so forth.
11 Better saves: Save as Fighter 2 (3, 4, etc.).
12 Armored: They have random pieces of armor on them. +2 to AC every time this comes up
13 Paralyzing touch: Save vs. paralyzation or paralyzed for 1d4 (1d4+2, 2d4, etc.) turns. Elves and anything bigger than an ogre are immune (might change too, if it is rolled again).
14 Hit the head: They can only be killed if you destroy the brain! Using the rules I proposed for aimed hits I'd go for 12 hp damage needed to annihilate a standard zombie ((3 x 2hd) + 6 (AC, because brain is protected by skull)). This comes up again, it needs one more point of damage every time. Damage to the rest of the body may immobilize it, but doesn't kill it.
15 Fear effect: They look much more disgusting than other zombies! Save vs. spells (-1, -2, etc.) or don't fight them for 1d4 (1d4+1, 1d6, 1d6+1, 1d8, etc.) rounds.
16 Regeneration: Whatever forced them back to unholy live wants them to stay that way. They regenerate 1 (2, 3, etc.) hp per round. Damage from holy or magic sources or from fire can't be regenerated. Finding and destroying the unholy source responsible for the undead, destroys the undead raised by it too.
17 Diseased: Taking more than 6 (5, 4, 3, etc.) points of damage from those zombies could result in a disease. Save versus poison (-1, -2, etc.) or random illness (DM's choice).
18 Exploding: Death blow makes them explode because of the gases inside (or because the evil spirit bursts out of them, etc.). Gory damage is 1d4 (1d4+1, 1d6,, etc.) in a 5 (+2 every time it comes up) feet radius. DEX negates.
19 Remembering: Basic motoric memory (INT +2 up to INT 7). A zombie might remember or possess something dangerous/useful (1d6: (1) level 1 spell (defensive), (2) level 1 spell (offensive), (3) level 2 spell (defensive), (4) level 2 spell (offensive), (5) magic weapon, (6) magic item) and is able to use it. 1 in 20 (1 in 10, etc.) zombies can do that. Those make expensive trophies for collectors or pets for zombie masters...
20 Strange origin: Roll 1d6 to determine: (1) parasite in humans, (2) plant infection in humans, (3) fungi in human, (4) animal, (5) humanoid, (6) monster. Roll one more time for special enhancement (and keep rolling if it comes up again...).
Rolling 5 times on this table should result in a zombie variant that is not too strong, but a challenge for low to mid level characters. With about 10 times it gets messy. Ghouls are a possible result by design and many effects complement each other (10 would alter 14, for example, either by adding 3 to the damage needed to destroy the head or by adding a hd with the same result).
* For every level a zombie master has, he can choose one alchemist/magical alteration for his zombies (just choose or roll).