slippery, tricky -- (not to be trusted; "how extraordinarily slippery a liar the camera is"- James Agee)
catchy, tricky -- (having concealed difficulty; "a catchy question"; "a tricky recipe to follow")
crafty, cunning, dodgy, foxy, guileful, knavish, slick, sly, tricksy, tricky, wily -- (marked by skill in deception; "cunning men often pass for wise"; "deep political machinations"; "a foxy scheme"; "a slick evasive answer"; "sly as a fox"; "tricky Dick"; "a wily old attorney")