Xcom2 Hints & Tips from Jon "Merlin" Malan

Don't you just hate it when you are chasing down a UFO or sub and your
interceptor runs out of fuel?  Here's how to exploit a natural bug in the
game and let your interceptors stay airborne for several months at a time:
Make sure that it is completely repaired, refuelled, and rearmed, then transfer 
it to another base (This requires a free hangar at that base).  As soon as it
arrives, it should report "ready" to launch.  Launch it to a waypoint of your 
choice, and then check its fuel--it should read 0%.  You can now stay in the air
as long as you like, because it has already passed the "low fuel" threshold.
To keep it "magic" like this, simply remember to give it a "patrol" command 
after any interception.  I usually don't do this much until I have sonic 
occilators/ plasma cannons on the interceptor, because those 6-shot missiles go 
really fast when you have unlimited "hang time".

Tired of always knocking out those hard-to-kill mutons or lobstermen instead of 
getting the kill points for them? Afraid that Chryssalid/Tentaculat is going to 
wake up and turn your favorite squaddie into a zombie? Shoot the unconscious 
goon with explosive ammo or just toss a grenade its way.  This is also a good 
way to get new rookies their first "kill" points.

Xcom 1 only: Even though the manual says you can't acces the items & equipment
screen of mind-controlled aliens, there is a way around that. Go to one of your 
soldiers' equ. screen and click on the right/left arrows until you get to the 
alien in question. Its picture should be a blonde male rookie with no armor, and
with all of its grenades & clips stuffed into its left leg pocket.  Now you can 
disarm him completely, grab a grenade, arm it, and drop it for Hari-kiri, or all 
kinds of other tricks.  My favorite is having Cryssalids grab a med-kit off the 
floor and go around healing my soldiers.

Xcom 1 only: beware of entering a skyranger mission when you have a minimized 
interceptor window going. It has been known to crash the game after the mission 
ends.

Xcom 2 only: Aliens on a floor just above you causing you trouble or blocking 
the only elevator? fire a disruptor pulse launcher or a thermal shock launcher 
straight up into the ceiling.  The blast will hit only the floor above, leaving 
you unscathed.

Xcom 2 only: Here's an unconventional way to enter the larger subs if you have 
Mag. Ion armor: look for overhanging corners that take up exactly half of the
map square. Stand directly under one, and go up.  You will be partly in, partly
out of the sub. From here you can walk right in through the wall, but you can't 
go back, so be careful.  You can even go up multiple floors on ships like the 
Dreadnought, bypassing the winding passages and taking a shortcut to the 
command center if you like.  This is especially useful for taking out a pesky 
alien commander who is hitting you with M.C. control all the time.