Vanilla Cuisine Royale..Jumping insanely high while hitting people with a frying pan for an instakill! Honorable mention to Radical Heights (no longer developed) that had the best ever lobby, where you could chill out doing different bicycle stunts.
My favorite shooter is Quake 1. I return to the game regularly and it still provides me tons of fun. The gun play, level design and character movement are of top notch and hardly any shooter reaches this level of quality. I prefer to play using the QuakeSpasm source port with some console tweaks that make this version of Quake close to the original unaccelerated version but with modern resolution support. It's an old game. I recommend it however to every FPS fan. If you haven't played Q1, you just have to do it. It's a timeless classic!
MY fav all time shooter? Doom 2. Easily this one. I've been playing this game since 1994 and in the last few years i've been playing an hour of it on saturdays and sundays. Not so much Doom 2 itself, but the community wads. The Community has been going strong and delivering a hell of lot entertainment that puts IDs work to shame. Currently playing Interceptor 2 and its a massive improvement over the first one. But its not just the maps, its also the weapon, sound, graphic mods that make it truly shine. Hell some of the wads were probably some of the best thing i played in some years. Wolfendoom Blade of agony, Adventures of square, Brutal Doom etc have been real highlights.