Good attempt, spoiled by lack of realism, e.g. squids do not exhibit the trademark bounciness that makes them such a deadly weapon in real life. Also, it has been all but proven that shark guns are unable to function properly during a zombie-nuclear combopocalypse, hence their phaseout by NATO in 1987-88.
Other than the above crippling flaws, great work! I love that you keep producing fun, original games that are all connected by a certain Nerdookiness. Can't wait to see what madness you've got for us next.
Great game! I have a suggestion: "fastest" targeting mode should take into account whether the target has been slowed or stunned, so that units with slow/stun abilities will spread them out instead of re-freezing the same guy repeatedly while his fast buddies run by. I also agree with 16779846541's request for "closest to exit" targeting mode, which is how most tower defense games work.