Rug

Source: Paizo Blog

A creature can spend a standard action to attempt to pull a rug out from under creatures standing atop the rug. This requires a DC 15 or higher Strength check, depending on the size of the rug. If successful, each creature standing atop the rug (some of its space must be on atop the rug) must succeed on a DC 12 Reflex saving throw or fall prone. Creatures that cannot be tripped are immune to this effect. Rugs that are larger than a 4-square area require higher Strength checks. The DC increases by 2 for every additional 2 squares of rug area beyond 4 squares.