12 Days
OK, this game was a blast. Literally. As in, blast the targets and watch 'em bleed. If you like shoot 'em ups, mixed liberally with gratuitous violence, this is a game for you. It's called 12 Days, and you can find it in the 'sniper games' collection at Freewebarcade.com. It's definitely worth a look.
The main difference between this game and other sniper games is in the graphics. 12 Days doesn't just do the basic stick figures; the graphics in this game are full color, moving, fairly realistic. The game interface gives you a basic wide view of an area, and you can zoom in, with a smaller rifle-scope view, to take your shot.
Like many other sniper flash games, this one is embedded within a story line. Honestly, I could have done without the story line; it wasn't very good, in my opinion, and it's main purpose was to set up the scene, and present you (the player/sniper) with a scenario and a mission. Hints to solve the mission are given in the story sections, but the game's authors could easily have just presented the hints in a simple mission briefing format, without taking anything away from the game.
All of that said, you should set your morals aside before playing this one. The story line makes you a Russian mobster's favorite sniper, so you can imagine the sort of missions you'll be getting. You rarely get more than one or two shots to complete a mission, but if you fail, you can choose to redo and keep the game going.
I give this one a thumbs up; it was a fun waste of time, and some of the mission hints were pretty tough to figure out. And every now and then, you just have to shoot stuff to feel better. It's a little more socially acceptable to do that on a computer screen than, say, on a bell tower, isn't it?