Shadowrun Anarchy: The Leviathan
In Shadowrun Anarchy, your post is called a "Narration". During your post you can not only control your character, but also external things, such as NPCs, the environment and introduce new story elements. If you want do something that would, within reason, require a roll, then make the appropriate roll (don't forget to add in the effects of your Shadow Amps and qualities), trying to exceed equal or exceed the target number of hits that have already been pre-calculated for the scene. Then, narrate the outcome! This means that you don't need the GM to move things along. Don't worry about 'breaking' the plot.
If you don't want to narrate the outcome (you feel it's important enough that you want be surprised or aren't sure how to resolve it), or feel as though the stuff you're trying to do isn't covered by listed target numbers, I'll step in and do GM stuff (e.g. describe the outcome, or you the specific target number) also indicate which scenes where I'll be narrating outcomes in.
A) Build off the narrations of other players, rather than negating them.
B) Avoid introducing too many wacky elements (such as dancing purple elephants)
C) Don't control other PCs or say what they will do as part of your narration. (Chat, discuss and engage by all means)
D) Use plot points to modify the outcome of your dice rolls
E Be aware that other PbPs may not support the entire shared narration thing.
F) Avoid instant win rolls
Mr Johnson: "I've hired you shadowrunners to find out who kidnapped my daughter…"
Burke spends a 1 Plot Point.
Burke's eyes flash with realisation: "Mr Johnson – you are the murderer!
Crap," Mr Johnson says.