I tend to alternate between Just Cause 2 and The Saboteur- JC2 for out and out mayhem, and TS for more sneaky pissing off the Nazis and leaving them looking around scratching their heads as I leap away over the rooftops giggling like a schoolgirl, before causing the next explosion that sends them into another frenzy. As already mentioned, Mercenaries was excellent for this too.
Outside that, quick deathmatches, preferrably with Instagib in UT99 or UT2004, or Perfect Dark/Timesplitters/The World Is Not Enough always quench my thirst for shooty shooty death.
Outside that, quick deathmatches, preferrably with Instagib in UT99 or UT2004, or Perfect Dark/Timesplitters/The World Is Not Enough always quench my thirst for shooty shooty death.