I was meaning static gun emplacements, using the guns we saw on one of the jaegers (which seemed to work against the kaiju).
Only the sheer stupidity of the military in this movie let them lose to the Kaiju. Bunker-bursting deep-penetrator bombs, depth charges (conventional and nuclear), low-yield nukes, drones capable of carrying low-yield nukes into Kaiju mouths, Kaiju-chomp bait with powerful conventional HE/nukes/futuristic plasma warheads to blow up Kaiju insides...there were practically a gazillion smart-aleck solutions to the Kaiju problem that the screenwriters were too dumb to think of!
Drones are a very good point. Now I have images of drones with tac nukes taking out the first few kaiju, with later beasts coming through with anti-air capabilities. That could be really cool depending on how it was handled.