Borked Hazard
- A single player mod where you play as a member of staff in a training facility for Bio-tec research.
- http://hosted.planethalflife.gamespy.com/borkedhazard/

Deliverance
- Reprise your role as Gordon Freeman in a story set after the end of Half-Life.
- http://blackbagops.com/halflife/deliverance/

Project: Quantum Leap
- Multi-authored, single-player Half-Life episode flouting any concept of continuity.
- http://www.unquenque.com/quantum/

Poke646
- A Half-Life single player modification with new weapons and other details.
- http://www.poke646.com/