May tip: I don't know if this one works so give it a try. As an engineer, use your railgun and shoot at the ammo room wall in the enemy base. I THINK that railgun nails go through walls so you could probably get a few easy frags from it.
April tip: As a pyro, whenever you are fighting pyro from the other team, always use your shotgun because he is wearing that armor that prevents him from catching on fire. Not many people know this trick so your odds of winning, unless you have low health, is in the 90s.
March tip: For some easy frags as a pyro, use your incidentary canon till you get to the enemy sniper nest. Then use your flame thrower to easily kill all the snipers. I read somewhere to do the oppisite of what I just said. I find it better this way.
February tip: To get rid of a sentry gun that is on the same ground level as you, run into the room, then throw a number two grenade (Any one will do.) at it before it kills you. If you got it close enough, then it should blow up.
January tip: This one is a tricky one. As an engineer, wait till someone comes out of the enemy respawn room and then run in before it closes. Then kill anyone there and build a sentry gun. Make sure it faces towards the room where all the respawning takes place. Because you're in a respawn room, there's ammo here. That means you can build it up to 3rd level fairly quickly. It is a good idea to have a partner of a stronger class with you.
December tip: In Mega TF, the best class to kill that fuckin' dog is an airscout. When near him, activate your jetpack and the flames would most definately kill him.
November tip: A very useful way to avoid getting blown away by some annoying soldier when playing as a sniper is to use a pattern technique. This is finding two or three places to snipe in and when ever you get killed or bored of being there, you switch to another place. This way that annoying soldier won't be able to find you as easily.
October tip: If you're an engineer, and you're surrounded by pipebombs, Just throw an EMP grenade at them. It will blow them all up. You wouldn't believe how many TF players don't know about this.
September tip: If you're an engineer, the best way to build a sentry gun to the 3rd level is to set it up, then jam all the shells you can into it and then go get more metal to upgrade it. Repeat this process untill it is 3rd level. Doing it this way will give you a 3rd level sentry gun with full ammo making only three trips.
August tip: When going against a soldier or pyro, always remember to stay away from the walls because if you stand next to a wall, and he misses, the splash of the rocket will do damage on you. So if you stay away from the walls, the only way to get hurt is if he hits you directly.