A thread where anyone can share successful strategies for making it to Round 10 or any of the other trophies.
EDIT: I earned the Never Give Up trophy today with a mic and a good coop partner, Matticus182. If it helps anyone, here was our battle plan:
Rnd1: Money (one player gets all $350k of money)
Rnd2*: Weapons (both get launcher)
Rnd3: Money (other player gets all $350k money)
Rnd4*: Supplies (both get mines)
Rnd8: Weapons (by far, this was the most difficult of the nine rounds we completed)
Rnd10: (didn't make it very far, but tried the weapons route again)
Order of upgrades: 1) Partial rifle (3 rate, 4 power, 2 clip), 2) Mines (full), 3) Launcher (full), 4) Flares (full), 5) Rifle (full).
(After these four, upgrading additional weapons was not very helpful. My coop partner had little luck with the shocker and blade cannon. I upgraded the flamethrower's range to use as a stalling mechanism, but this unfortunately will light half of the screen on fire. The new auto-turret "may" be worth it, provided you can get through the Supplies route on Wave 6 which could be very risky.)
My Total kills: ~3,500
Total time: ~1 hour and 30 minutes (according to in-game records)
* The only thing in hindsight that I would change would be to do the Mines in Round 2 and then do the Launcher in Round 4. The reason is that I perceive the Supplies Route to be more difficult than the Weapons Route (on coop, the opposite can be said for solo). It could arguably make things easier for you in Round 4.