32nd!
I love the variety of weapons and the core gameplay. I would weigh your options of having the cycle of weapons be predictable or randomly determined (i.e. being able to count on a duck bomb, or getting a duck bomb randomly).
I'd love for there to be more sounds for the little things -- zipping around on the line, scientists screaming, glass breaking when it's shot out -- there's a lot of potential even with what you already have.
If this were an arcade cabinet, I would lose a lot of quarters to this bad boy getting my initials up on the leaderboard. Outstanding!