As pointed out by others, the first three minifigures are genuine LEGO (with the second having perhaps a few custom accessories). The fourth is not a LEGO minifig. It may include some genuine LEGO elements (legs, hands, etc), but the militaristic accessories are not LEGO elements. This appears to be a custom minifig sold at one time by Modern Brick Warfare.
The head is 3626cpb1091 AKA "Nightwing with red eyes". It only appears in one set, 76011-1 Man-Bat Attack:
The torso is 973pb0714c01 AKA "torso witch with green belt". It only appears in set 850487-1 "Halloween Accessory Set" and as a collectible minifigure from Series 2:
The legs seem to be plain black legs, way too common to ...
The figure holding the lightsaber is composed of the head and hair of Anakin Skywalker from the Clone Wars series:
the torso of Luke Skywalker as a Jedi Knight:
and a pair of dark gray legs on medium gray hips:
The clone figure has the torso of a shock trooper from Ep 3.:
But I couldn't find the helmet.
Zovits identified most items, the missing helmet is a Stormtrooper Type 2 helmet from an AT-AT driver, which is likely also where the legs from the Anakin/Luke mix figure as identified by Zovits come from.
As an added bonus: the torso of this AT-AT driver is used on the middle stormtrooper on the second row from the front, so you have the complete figure.
I talked to a Lego expert on the lego.com online chat. He told me that this particular lego head was an exclusive part for the Build a Minifigure bin and gave me the part number for it 6257472 mini figure head #2829. I didn't know there were exclusive parts in the minifigure bin, I wonder if this is something new. He seemed quite surprised when he found ...
These are identified from left to right.
Series 18 of Lego Minifigures has that first policeman. Here is the exact minifigure.
The second one appears to be from Series 9 of Lego Minifigures. Here is the exact minifigure.
The third policeman appears to be LEGO Policeman with Riot Helmet Minifigure with a different head. The head might be Minifigure, Head ...
this appears to be
Robot Devastator 4 - Red Eyes
from the following sets
8107: Fight for the Golden Tower
8112: Arachnoid Stalker or 8115: Dark Panther
Partlist for Devastator
Bricklink part list
The leftmost one is Black Widow - Black Hands from 6869 Quinjet Aerial Battle:
The second has a pair of generic grey legs and the torso of Snake Oiler:
The middle one has the legs of Blackbeard from the Pirates of the Caribbean:
And the torso of Hector Barbossa:
The fourth one is Dengar from Star Wars with different hands:
The rightmost one has the ...
48379 is the part number for the torso piece. 2003 would be the copyright date for the LEGO trademark.
They are both promotional items which were distributed with McDonald's Happy Meals.
Bricklink: 7923-1 (White Soccer Player #4)
Bricklink: 7917-1 (Blue Basketball Player #22)
You can find all the minifigs heads ever made, with the date of release, in the BrickLink catalog: http://www.bricklink.com/catalogList.asp?pg=1&catString=238&catType=P&v=2
Please note that I have already sorted the minifigs heads in the link above by year released, however on the first two pages of the results you will see heads where the year ...
First is sw0603 "Shadow stormtrooper", with Lord Business' hair (from The Lego Movie).
Second one is sw0258 "Hoth officer", possibly with a different head.
Third one is loc002 "Razcal from the Legends of Chima line.
Fourth one is sw0581 "AT-AT driver".
Yes they are. The top figure is made out of these parts:
Head: Item 3626bpb0220
Hair: Item 3901
Torso: Item 973c19 but with yellow hands
Legs: Item 970c00
The bottom figure has the same torso as the top figure, and these parts:
Head: I cannot find this as a LEGO provided minifig head print, but there are several ways to customize LEGO heads, like ...
Legs and torso are from a Unitron figure: http://www.bricklink.com/catalogItem.asp?M=sp048
The red bandana has appeared in almost 100 sets (often pirate-themed), while the head and hands are generic and could be from any number of sets as well.
Same as in OP's other minifig identification question, the answer lies within set 75828-1 "Ecto 1&2".
The minifig is gb020 "Mayhem". If I remember the movie correctly, this is the ghost that interrupts the rock concert.
Knight's Kingdom II - the guardian (picture taken from bricklink)
I searched on Bricklink catalog under, 'minifig leg assembly' using the keyword, 'brown,' using thumbnails. Only had two pages to look through.
Looks like the Comic-Con 2012 exclusive Shazam / Captain Marvel: https://www.bricklink.com/v2/catalog/catalogitem.page?M=sh042#T=I
From the quality of the lighting in the photo it's hard to be definitive but if I had to guess I'd say this isn't genuine Lego but a reproduction figure or knock-off (KO).
At last, I have your answer. The figure is from a "Giant Pre-School Loc Bloc" set, likely the "Playground" one shown in the picture.
Nearly a month later, while doing unrelated research, I found "Giant Brix Blox", a second possible source of these types of figures;
It makes since given that sources claim Loc Blocs & Brix Blox were both imported ...
The torso for this figure is 973pb0321c02 Torso Town Vest with Pockets and Striped Tie over White Open Collar Shirt Pattern / White Arms / Yellow Hands.
It comes in several minifigures, but none of them are like yours, so I think this is composed of other parts ( a MOC figure) and not directly from a set.