gun towers are freaking AWESOME. They're cheap as hell in their base form, cheap to upgrade, and deal grievous amounts of harm to anything when you place them in packs. I hoped for a specific entry in TVTropes for this type of weapon, but couldn't find it. Basically, it's the kind of thing that is the lightsaber in Jedi Outcast, the disc in Tron 2.0, or the Predator in Shadowrun (Genesis) - a weapon you get early on that is basically the best thing you can get in the entire game. Now that I know how awesome gun towers are, I've gone from simply wanting to beat levels to only wanting to finish levels without a SINGLE core taken, and it hasn't been too much trouble between spamming gun towers, placing one or two temporals, and a couple of meteors. And maybe some missile towers for airborn enemies, MAYBE.