Not too bad, but there is room for improvement...
The music was one of this flash's best points. It sort of was, well, appropriate for a murderous rampage!
The part where Mario stole the tank got ridiculous, but I liked the ending. I liked it when it said "MONSTER KILL!" and stuff after he killed a lot of people.
It could have been a bit funnier, like if Mario shot someone in the balls or he threw his gun at them after he ran out of bullets or something.
Pros:
1) Authentic Mario sprites and cool effects
2) Good ending
3) Awesome music
Cons:
1) Cheesy tank scenes
2) No interactivity
3) Not very humorous