Damn this heat and my fragile body!
Cheating in regards to a test and/or assignment - yes I have back in high school and frequently.
In senior high school exams (state assessed/HSC) and University exams. Not once did I cheat - the penalties are far to excessive to make the risk of cheating worth while.
On to more 'interesting' cheating.
When it comes to a partner - yes I damn well have cheated on some.
It was in retaliation to what the partner had done to me at the time and lied or ommited to at least tell the truth of what they'd had done. It was sweet revenge to not only to do to them what they had done to me - but to be totally honest about it and not hide it at all.
It's not the cheating part that stings - more the false representation. Whats the point of impressing on your partner - that they want a commited relationship and they specify that fidelity is a big part of the deal. Only to have them some 2 months later see their ex behind my back (and there was no doubt of what was going on). Then to keep it from me and not be honest (I'm not the only person to have been placed in this situation, nor is it restricted to one gender). Both genders are just as bad as one another in the relationship stakes on the whole.
All you can do is be honest about what your expectations are. To some fidelity is important - to others it's not.
The least your partner can do is be honest about what they expect from you and receive honesty in return - so at least you can go in eyes open as it were.
But if you want to play the field - then 'two' can play that game.