- Momentum and Reversion portfolios based on ranking alpha factors - this is still in its earlier stages with simpler factors being used
- Pairs trading using Bollinger Bands and 2 sigma test. Many players have started to use co-integration instead of correlation
- Some basic use of ARCH/GARCH models in the options space
- Volatility arbitrage.. with poor gamma management
- Order-book balancing
- Automated standard technical trading systems
- All manner of arbitrage strategies
This isn't a comprehensive list.