I am starting a new poll, to see which BTD5 tower upgrades are the best. Credit goes to DragonFiire (blocked).
Pineapple Division: Top 2 will advance to next round. Note that Artillery Battery has been removed from the original (since Mortar is in the original twice).
Ray of Doom
Super Wide Funnel
Banana Research Facility
The Big One
First Strike Capability
Bomb Division (Added so all towers can be represented):
High Energy Beacon