The Collaborative International Dictionary of English v.0.48:

Wittingly \Wit"ting*ly\, adv. [See Wit, v.]
   Knowingly; with knowledge; by design.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "wittingly":
   advisedly, by design, calculatedly, consciously, contemplatedly,
   deliberately, designedly, eruditely, in cold blood, intelligently,
   intentionally, knowingly, learnedly, meditatedly, on purpose,
   pointedly, premeditatedly, purposefully, purposely, purposively,
   studiously, understandingly, voluntarily, willfully,
   with forethought, with full intent, with intent,
   with malice aforethought, with purpose