Here's an opening gap strategy I tried out on apple. The model looks at the gap from the previous close to the open and makes a trade if this is in the opposite direction as the long-term trend.
Overall I think the strategy is alright but fails to work with other equities, does not scale well and may be susceptible to overfitting. Additionally I think it is possible that the default transaction costs could be understated in this case. It would be nice to see this tested on a small basket of HIGHLY liquid stocks.