Dwarf Fortress

From the wiki:

A list of DFHack commands that can help with your framerate by fixing bugs and reducing items.

• autodump Useful for mass dumping or destroying items. Use help autodump for options.
• cleanowned Confiscates and dumps garbage owned by dwarves. Use help cleanowned for options. Can cause unhappy thoughts if no replacement clothing is available.
• clean and spotclean Removes contaminants from tiles/units/items or one tile. Bug:296Bug:1750Bug:3270 Use help clean for options.
• flows Counts map blocks with flowing liquids, which slow the game down.
• tweak fast-heat Further improves temperature update performance.
• timestream alters the game simulation speed so that it feels fast even at low FPS. Either the calendar, or the units themselves, or both, can be changed - so timestream -fps 100 -units while your actual FPS sits at a measly 20 will make the calendar tick and the units move five times faster. This is very useful to extend the playability of older forts where early micromanagement isn't as important and most of day-to-day functioning runs itself.
• fastdwarf Causes dwarves and other creatures to move and work faster or causes them to teleport. Run fastdwarf help for more information.