I know FPSes are all the rage these days, but I really think one shooting-based genre that is severely underrated is the third person shooter. I must say that I am a bigger fan of TPS than FPS, and I recently got ahold of Jet Force Gemini, an N64 game by Rare that I always wanted to try. Project Eden for PS2 was also added, since it was described as a cross between a TPS and action-puzzler ala The Lost Vikings (which is awesome). Some of my favorites in the genre include Fur Fighters (DC/PC/PS2/IPad), Metal Arms: Glitch in the System (GC/PS2/XBOX), both MechAssault games for Xbox and even Tomb Raider which incorporated many TPS elements.
I'm also looking to try P.N.03 for Gamecube, and Gun for Xbox, which has a Western theme.
Also, what would you consider to be examples of good 2D TPSes? I ask since it's a largely 3D genre.