A few days back, I discovered a cool entity on the toybox in Garrys Mod. It was an ammo crate that gave you unlimited ammo for any weapon. A word of warning: spawn a radio or something whilst you are holding the use key. It takes a VERY long time to get 9999 ammo on everything. my favourite weapon is the FiveSeven on the game. For dealing with shit loads of hostiles, use the RPG. Or a grenade. if the hostiles have weapons, they will scatter across the map. Love doing it with Hannah montana hostiles. She's usually blown to pieces before you can say 'the best of both worlds'.
Two of the annoying entities is Dr Haax and Fleming, who says 'HI!' and slaps you repeatedly. Warning: do not spawn shit loads of these two entities. It will hurt like hell when they attack you. I suggest using god mode for this. And getting the haax swep to kill Dr Haax is a good idea too. He can be killed by close range RPGs as well. It is really hard to kill Fleming. Tried the 'It's a Trap!' swep as well the baseballbaterizer or what ever it is called and frankly, he is annoyingly invincible.