Let's play a little game called "SVU brings in loose cannon outside detective to show that they (*cough cough Stabler*) aren't so bad!"
Redemption: It was covered earlier here, but the synopsis even says "Detective Stabler is paired with John "Hawk" Hawkins (David Keith), an unstable, "cowboy" cop, much to Benson's chagrin."
Pandora: The homicide detective working with Elliot was quite harsh while interviewing a young girl and later roughed up a suspect in interrogation.
Dominance: We've seen Det. Dave Duthorne (sp?) a couple times; in this instance he really blows his stack after arresting one of the suspected brothers and holding a gun to his head (Fin has to call him off). Also roughs up the other brother later on in interrogation, but that was "only" standard, run-of-the-mill stuff.
Escape: The deputy marshal Olivia worked with (and used to date) had some cowboy moments.
Fat: Anthony Anderson's detective from Queens SVU (before he joined the mothership as a different character) was quite animated, tried to lie to a teenage girl to get her to talk, and even physically fought Stabler. Cragen later says that he paired the two because he wanted Stabler to get a glimpse of someone who crosses the line like he does.
Baggage: Victor Moran doesn't play well with others and also repeatedly kicks the perp once he's finally caught for good. Semi-understandable because he was dealing with the turmoil of losing his wife and eventually his daughter, but still.
Unstable: Maybe the most appropriate example, as even the title feels like a nod to the "Unstabler" moniker some fans placed on Elliot. Anyways, after being introduced to Officer Nate Kendall as he's shoving a pistol down a suspect's throat, he gets dragged into a SVU case. Kendall barrels through it like a bull in a china shop, all while not exactly following standard SVU protocol. At the end, he may or may not have tossed the real rapist out the window (a later episode acknowledged it as a suicide).
Feel free to add more.