Bonus Checks - keep them for you - tell her you got 1/3 of what you thought, and play with the 3/4 left.
RRSP returns - have a deal with her that you and her get to do what ever you want with them.
Independent Vacations - she gets a girls vacation, you get a boys vacation - but YOU dont go on your vaction, you save your money for hobbying, and live in a fishing hotel eating beans for a week, instead of a luxury hotel, like she will.
Take a 100 cash a week for fun money - but only spend 30. Takes longer but it's easier then getting busted.
The Costco idea is pretty good, except she will ask, what did you buy ? And where is it ?
Christmas is the one time a year that woman dont' tend to ask about money leaving accounts. JUST take out more now then you usually do, and save it.
Buy a vending machine - it's all cash - and never tell her about it.
Start doing cash jobs, and tell her you are working over time. But as we all know, overtime doesn't mean more money on our checks.
Start doing all the accounting yourself, both accounts.
Get a seperate credit card, that is mailed to a P.O box and use it for cash advances. Yes the interest rate is higher, but in the long run it's worth it to not have a looking glass in your accounts. This only works, if you are not planning on any large purchases together as it will show up with a credit check.
STOP implusive spending on stuff, and save it for us girls.