I could have chosen. I could have said: we play straight B/X, Labyrinth Lord, Holmes D&D or Lamentations of the Flame Princess maybe. At the opposite extreme, I could have laid my own house rules bare and send them all over the web through this Lulu guy. At some point, owning most retro-clones and original rules, I found myself wanting to choose too many mutually exclusive rules at the same time and I was like “what exactly are we playing?”.
I've got now the answer: we grow up, empower ourselves and play everything we love. We're playing elves as character classes if we feel like, next to an Advanced Edition Companion, or AD&D or whatever elven fighter/thief, we're playing the spells and magic system from Lamentations of the Flame Princess with Dark Sun's Dragon Kings spell casting weird effects, we're playing Holmes initiative, PHB assassins and bards, jesters from Dragon and White Dwarf houris.
The first session my players sat in, they began like “come on, don't tell us we play 1st level again, make it a two” and, to my — and their — utter surprise I went “sure, cool. Now give me those oreo cookies, please. Oh and, while you're at it, eject this Guild Wars, Apocalyptica and Conan OST we've been playing with for too long, and play the last VNV record”.
So did we begin The Great Scum Hack, an adventure set into the Rudingoz random city I'm designing at the moment. It's called “hack” because this introductory adventure shows a way to hack the random city and to play it, say, reverse engineered. I can't think of any better way to write an introductory adventure to a setting/campaign than one that makes it lie from the beginning, it's so boring to wait 12 sessions until a bit of the secrets get revealed anyway. It's also called “hack” because this adventure was originally designed for Rackham's Cadwallon RPG, but disappeared into the nether void when the publisher went bankrupt or so. I was paid good money to design it in 240 pages and it's now 16 pages, going to be cheap and way better.
But it's not the only reason why it's a hack, it's also because there's everything OSR inside when I run it. Characters starting money, physical traits, background skills, contacts and enemies are ripped from Lesserton & Mor ; shop keepers, dead bodies, NPCs and fortunes are from Vornheim ; most magic items come from Goblinoid Games' Realms of Crawling Chaos — or Deep Ones if my players feel like playing one some day — temples and events come from the Classic Dungeon Designer Old School Encounters Reference #4, etc. I could go like “oh you've printed Nicolas' Orc and you want to play one? Let me think about how to make it fit, I'll find something”.
Of course, you're not gonna need anything else than a rules system and the booklet I'll Lulu to run it yourself but if there's something you or your players love anywhere, whether in Stars Without Numbers, Red Planet, AD&D2 Al Quadim, the Hill Cantons Compendium, whatever, just do like I do and get your fun.
One last word: it's not Gonzo, not at all. The universe this all shapes has a very, very strong suspension of disbelief, it's almost seamless, it's rock-solid as a good book saga. Yet, of course, I'm lucky not to play with any rules lawyer or setting expert. What about you? Is your game a megamix as well? Why not?