Making the Game Harder (Apocalypse)
Write here your suggestions about how to make Apocalypse harder to play.
No Money Exploits
There are a few shady ways to gain money such as with stripping Stormdogs or messing with the engineering screen. It kinda goes without saying but don't do that.
Real Time Only
For those of you who only use turn-based play, while some consider it easier, it also involves a lot of thinking and reactions on your part and thus allowing for a more interactive, and in some place harder game play.
In contrast to the Real Time Only you can play in only Turn-Based Combat, this instantly makes a number of aliens a lot more dangerous, especially if your men have low reactions as the Brainsucker and Popper can run up to your men and Brain-Suck you or explode in your face without your men being able to react like they can in Real Time.
XCOM can only investigate the alerts given out by Megapol. Prepare to have many organizations taken over by alien influence and beware losing the senate. Some luck is required for this mode because the city starts heavily occupied by aliens and alerts are wholly inadequate to manage the panic. Note that you can prevent drops by destroying UFOs before they reach their target.
No Humans Allowed
You can never use human soldiers in combat. Fire the soldiers you start with. Start recruiting from SELF and the Mutant Alliance ASAP. Both soldier types are fairly uncommon but for an extra challenge you can opt to only use androids or only hybrids.
Senate Funding Only
This is basically in the same area as the Council Income Only in UFO and TFTD. You must rely on the Senate's Funding and selling stuff. Unlike in previous titles a huge chunk of XCOM's funding comes from the Senate, so this mode isn't as tough as it sounds.
Don't Raid Other Organizations
You can not raid organizations for their phat lewt. This will be rough especially in the first few weeks as XCOM starts on a tight budget and raiding is the only other source of income. After a few weeks the Senate's income grows enough that you can manage.
Don't sell Artifacts
Don't sell any alien tech. Mod all alien artifacts to have zero value if you must, or sell it before it gets a price tag from research. Alien tech does pile up in storage after a while so be sure to blow up bodies and make judicious use of "abandon battle". You don't really need the huge surge of artifact money to beat Apoc in any way.
Don't sell anything. ANYTHING.
For an increased Challenge, don't sell anything at all! This will hurt badly when upgrading to the Air Hawk, and you will not be able to manufacture for profit nor refund anything you don't like. Also be prepared to manage the huge amount of JUNK that will pile up in your storage, perhaps by abandoning it in battle! Remember that alien bodies are incinerated and not sold so burn away.
Unlike in previous XCOMs the starting equipment never really becomes obsolete. Arthropods and Skeletoids are featured the entire game and they can be killed with machine guns or autocannons all game long. UFOs can be destroyed with conventional missiles, while top tier UFOs are still manageable with elerium guns and tanks. Megaprimus definitely gives everything you need to beat the alien menace so go give it a try.
Human Tech Only
You can not use any researched alien projects. No disruptors, no shields, no vortex mines and so forth. This mode does not preclude XCOM from building the hybrid craft needed to breach the alien dimension, but you can not equip them with alien tech like shields or disruptor weapons. On the plus side this saves you a lot of trouble having to research them!
The Toxigun is the single most powerful weapon against the alien menace. So don't use it. Even alien gas is more fair than the Toxigun.
No Stun Grenades
Stun Grenades are good. Like REALLY good. They can KO brainsuckers as they hatch, get you early game shields, or prevent Multiworms from breaching their offspring. Give yourself a challenge and don't use them.
No Disruptor Armor
First you restrict your weapon selection and now this! Megapol armor is pretty good but expect a return of the mortality rates you are familiar with in UFO/TFTD.
Don't ever let an agent or vehicle's health bar turn blue. Shields are so good they had to be mentioned twice.
Hoverbikes are one of the most effective combat vehicles early in the game and they can serve you well into midgame. Sell them off and start using the other vehicles instead.