Here's where I think things get tricky with Warrants held in a TFSA....

No worries if you buy and sell warrants...they're bascially a futures contract, like call and put options.  You buy a bunch of warrants at 50 cents (or whatever) and they sit in your account.  Then RVX moves to we'll say $3 in another 6 months...putting the warrants well into the money, and now they're maybe trading for $3.50 each because of the time value of money thing....they still have 3.5 years left until expiry.  Rather than excercise you could simply sell the warrants inside the TFSA, and the gain you made is not taxable.

But if you decide to exercise the warrant....if you have say 500 warrants, that's $2.05 x 500 for a total of $1025.....I don't know if you're allowed to do that.  If you are I would have to assume that the $1025 would also have to come from money within the TFSA.

Just guessing, but I think simply selling the warrants would be easier....although probably a little less profitable.