I like the LHS = RHS ones which involve the more complex trig. identities like 1 + tan^2 = sec^2 or some variant where it's not as simple as "oh okay, well cot is cos/sin and csc is 1/sin and sec is 1/cos, plug that in, simplify, oh look i get 2 = 2 or something"
At least try and trip up the...