Good game.
Leave a few more options open for yourself, like having three different settings for difficulty or whatever. Also instead of the space bar maybe on the more difficult settings you couls make it a left click on the target type of game?
Anyhow, the game was all right, but you know there are more victims ready to kill out there, maybe the ultimate shootout could be with the NG tank or something, and remember Tom and Wade love having their likenesses used as well.
A last thing to consider is (for really tough targets like the tank and Sack Smash) maybe you have to shoot the target a couple of times or in some really vulnerable location. Anyhow, I liked it a lot and think that what I have mentioned wouldn't make the game that much bigger for the most part, especially the difficulty changes part, that would just be altering timers.
Have fun and if you use any of the ideas, email me and I will come play the game and review it again. Laterz.