Overkill is a Xonotic mod focusing on fast movement, fewer but more powerful weapons, nades and respawning near team mates.
To excel at Overkill there are two things to practice: aim and speed. If you're feeling old or your reflexes aren't that good, don't despair, since speed is the more important of the two. Some of the best players focus on movement almost exclusively.
Every vanilla movement tip also applies in Overkill. However there is one key aspect making the game way faster - dodging. But let's review the basics first:
Same as vanilla - instead of just walking around you should always jump because it's much faster. Basically keep the jump key (by default space bar) pressed all the time. The are only two exceptions to this rule:
you want to be slow (to not fall off a ledge)
you need to sneak, since bunny hopping makes a lot of noise (you can crouch additionally to further minimize your movement noises).
The turning and strafing tips also apply: hold forward to move straight, release forward and press left or right while moving the mouse slow but steadily in that direction to turn.
Laser / Blaster
All weapons in Overkill have the same secondary fire - laser (sometimes called blaster). It pushes the player using it (and also flags and nades), but unlike in vanilla it doesn't deal any damage. So blast away, literally.
Its main uses are:
jumping higher - just aim at the floor and shoot (video)
climbing walls - no matter how high, just keep shooting the laser at roughly 45° down against the wall
shooting nades or the flag on the ground to make them bounce a little - this is great for separating the flag and the nade when a killed FC dropped both.
When starting to move:
Dodging is Overkill's defining feature. When you want to start moving, quickly press forward twice. You must be completely still before this and it must be followed by bunny hopping or else you lose your speed as soon as you touch the floor again. (Press forward, forward, then hold jump - don't press jump before the first forward or it won't work).
You should do this every time after spawning because this is the fastest way to start moving. You'll accelerate several times faster than normally.
Dodging does not only apply to starting a movement, but can be used on every (more or less) smooth surface next to you. For example you can bunny hop alongside a wall and press the forward key in quick succession to gain more speed. You can do this multiple times with only a short cooldown time. You can reach very high speeds using wall dodging. Good maps to try this out are Tarx and Equinox.
The fastest way to accelerate is a combination of both wall-dodging and blastering. This can double your speed when done right.
Martin-t made a video containing all the above mentioned movement tricks with key presses shown: Link to video - middle click to open in new tab
Desperate times call for desperate measures. Sometimes you need to get away really fast. One way to do that is to let a nade (see the nade entry in the weapons section below) explode in your hand. This can be done by either facing in the opposite direction of where you want to be hurled or by being in the upward motion of a jump when the nade explodes. Space Elevator is a good map to try this out. You can see this in action in this video.
Since a nade does about 160 damage you need additional armor or health for this trick, otherwise you'd just commit suicide.
Every player has the same three weapons. You don't have to collect them and you also have infinite ammo. The only thing you have to care about is to choose the right weapon for a task and timing the reloads.
Vortex (also called nex, long distance, perfectly precise)
the main weapon, good in almost every situation
Shotgun (close range, with spread)
more damage than vortex but only in short range
faster rate of fire
slows enemies down - shoot them when they're jumping across a chasm to make them fall
Machine Gun (also called uzi, mid-range weapon with a bit of spread)
spread increases gradually, better shoot short bursts
also slows enemies down
can deal small amounts of damage through walls
great for removing armor shards from enemies, finish them off with a vortex shot afterwards
Two more tips:
Never reload in the middle of a fight. Switch to a different gun instead, it's much faster.
Whenever you're safe, reload. Don't run around with only a single bullet remaining.
Those weapons have to be picked up and are only available on some maps.
Heavy Machine Gun
this is like the machine gun - just bigger, faster, with a larger ammo capacity and way more powerful
point at general direction of the enemy, keep the trigger pulled, enemy dead
Rocket Propelled Chainsaw Launcher
this sounds more fun than it actually is, basically it's a rocket launcher
slow rockets (not very suitable for long range), huge damage, quite a damage radius
you'll have a hard time not killing yourself with it, so you better jump around while using it and not aim at walls next to you or the ground under your feet
Nade is the shorthand term for grenade. Nades deal quite a lot of damage in a large radius. Keep in mind they bounce off walls and fall down stairs. Due to their damage radius they even hurt players behind walls.
You can arm a nade by pressing the drop weapon bind (by default the g key). After that a countdown of about 5 seconds starts until the nade explodes. You have to press the drop weapon key again to throw it. You can throw a new nade every few seconds.
To excel at nading here are a few tips:
Keep the nade in hand until just before the explosion and throw it at an enemy. That way the nade won't bounce off and the enemy has no way to dodge it. You throw with more force the longer you wait.
You can use nades like a mine by dropping it on the floor at a place where an enemy will very likely be in a few moments (e.g. the flag spot in a CTF match). You can easily drop a nade without bouncing by crouching before releasing it.
There is another key bind for nades that works by holding the hook keybind to arm and releasing it to throw. Don't use that one, Overkill is too fast for it. You can't afford to keep a key pressed for several seconds. Use the drop weapon bind instead.
Jumppads usually works for nades, too.
You can also use nades like a rocket launcher by throwing a nade in front of you and then hitting it with the vortex. This propels the nade very far and causes very high damage with quite a bit of spread. It takes a little practice but is definitely worth the effort. Great for getting rid of campers or remote groups of enemies.
Watch this short video to see what it looks like: Link to video - middle click to open in new tab
There's not much to say here except take everything you get. If you think there's no reason to pick up items because you'll quickly die anyway, you're wrong! Without any pickups a single vortex hit will instantly kill you. So don't ignore items, even that tiny 5 armor shard dropped by a killed enemy will keep you alive and win you time to shoot back or get in cover. A fully equipped player (max health at 200 and max armor at 100) will sustain three vortex hits. If they don't come in quick succession even four, because he's probably gonna pick up a shard from a dead body in the meanwhile.
In a 1on1 game you should even pick up items if you're already maxed out. You won't gain any extra health/armor, but you deprive your enemies of that bonus making it easier for you. When playing in a team however you better leave the items for your teammates in need, especially flag carriers in CTF.
The small (5) shard is dropped by killed enemies. As noted above, it's more useful than it looks.