Another vote for Danger Girl. You’ll enjoy it, especially if you’re a Codename: Knockout fan. (I have an extra copy of the TPB, if you want to e-mail me!)
I’d also suggest Sleeper, although it is pretty dark and intense, without the comic relief moments of The Losers or the tongue-in-cheek sexiness of Danger Girl. It is my favorite comic right now, and I’ve already hyped it in other SDMB threads. There are two TPBs available, reprinting #1-6 and #7-12 of the first series (“Season 1”), and the series is currently on Season 2 #3. There is also a prequel, Point Blank (a TPB reprints #1-5, the entire miniseries), although it is more of a mystery than a spy story like Sleeper.
Spy Boy is very tongue-in-cheek but doesn’t adhere to the formula too much, though the irregular schedule makes it hard for newbies to find. Bombshell makes it worth the while, however.