This is another commentary on an OD&D mechanic I think was particularly salient: HP rolling.
My first experience with rolling hit points was in a dorm room freshman year of college. We had just hit level two in our AD&D game and I held the D6 for my half-elvish thief (who was still pretending to be a monk, I believe -- I don't think anyone else realized monks used D4s, luckily!) with trepidation. "This is the most important roll of the night!" I remarked.
Even that early in my gaming career, I knew that AD&D's style of adding HP upon level up had some issues. Namely, that a poor HP roll could be crippling for a character's entire career. Its quite possible for a fighter with 16 CON to hit level 4 and have 30 HP (average), 48 HP (max) or 12 HP (minimum).
Interestingly, in OD&D, when you gain a level instead of adding the new HD to the total, you roll all of your hit dice over again. You either use the new roll, or your old total, whichever is higher.
This leads to a gradual equalization between the fortunate and the unlucky. Namely, all you need to do is survive another level and you'll get another shot at a decent HP roll. You're not saddled with that "1" for HP gained forever. This ensures more predictability for characters at mid and higher levels, as you can ensure that they will hold more closely to the expected averages instead of being really low or really high.
The Next Step
I like the idea of using this sort of "growth" mechanic for other stats. For example, let's say you rated a skill from 1 to 7. At level up time, if you put a "skill point" into that skill, instead of just adding +1, you roll a die. If the die is equal to or higher than your current ranking, you add a point. Otherwise, its wasted. This allows you to randomly generate starting skill levels if you like, as you know that the poor will close the gap with the lucky in a few levels. It could also be used for improving ability scores (roll LEVEL + 1d6, or +2d6 if its your Prime Requisite -- use it as your ability score if its better than your current one).
I've already discussed using a mechanic like this for storytelling purposes (see "Survival Isn't Everything). Finally, I think this sort of mechanic might also work for wealth acquisition. If you find a stash of loot in the dungeon, everyone rolls 1d6 and you have the potential to increase on the "Wealth Scale."
I think this may not work for stats that can be spent down (like Wealth or even Alignment). Because players will know that they are getting diminishing returns and will spend so as to always be around a score of 2 or 3, tops. Now, this may be what you want (encouraging freewheeling adventurer lifestyle with lots of flagrantly unnecessary expenses) but it might also lead to wonky behavior.
OD&D Experience Levels
8 hours ago