Terms for subject Informal containing purpose

English	Russian
accidentally on purpose	якобы случайно (joyand)
at cross-purposes	на контрах (Agasphere)
for no purpose	ни за понюшку табаку
no purpose	зря
not without purpose	неспроста
on purpose	впику
on purpose	специально (e.g., we did it on purpose to demonstrate how we can ...)
on purpose	в пику
to no purpose	по-пустому
to no purpose	задаром