Sandpit is a sandbox mod for Half-Life. In Sandpit you can spawn monsters from Half-Life and Opposing Force as well as spawn and pose models from Half-Life.
Sandpit v3.2 (.zip) Extract to steamapps\<user>\half-life\ - Added a basic menu to manipulate spawned models and monsters. - Fixed spawned models not spawning upright. - Added lots of extra Half-Life content by Valve.