Per Wikipedia

1. A brand of fruit-flavored sweets, currently produced and marketed by the Wm. Wrigley Jr. Company,[1] a division of Mars, Inc. They have hard sugar shells which carry the letter S. The inside is mainly sugar, corn syrup, and hydrogenated palm kernel oil along with fruit juice, citric acid, and natural and artificial flavors.  The kind Marshawn Lynch eats ;)

Source: Urban Dictionary, Internet Slang, Yahoo Answers

2. Skittles (drugs)- can refer to MDMA (ecstasy), Dextromethorphan (Robotusin cough syrup), and a Skittle party is when young people raid their relatives medicine cabinets, place all the pills in a bowl, then pass them around, or play a game, taking a pill which you don't know what it is.  http://www.wsmv.com/story/23508683/skittles-parties-draw-concerns-of-prescription-drug-abuse

Source: Wikipedia

3. Skittles (bowling type game)- Skittles is an old European lawn game, a variety of bowling from which ten-pin bowling, duckpin bowling, candlepin bowling (in the United States), and five-pin bowling (in Canada) are descended. In regions of the United Kingdom the game remains a popular indoor pub game. A continental version is popular in Germany, Austria and Switzerland. Other varieties of bowling are more popular in Australia, but the similar game of kegel, based on German nine-pin bowling, is popular in some areas.

There seems to be quite a bit of variety in the particulars of the game.

4. Skittles-  varied description of the female genitalia, or it's functions, as referenced in songs by Iggy Azalea, and Beyonce.

Per: RapGenious, Urban Dictionary

Iggy Azalea-Pu$$y

[Hook:] Left right, back to the middle, Head on a swivel neck, till I quivel.   Open ya mouth, Taste the rainbow, taste my Skittles, ah!

Beyonce- Blow

[Hook]Can you eat my skittles? That's the sweetest in the middle.  Pink that's the flavor.   Solve the riddle.   I'm-a lean back.  Don't worry it's nothing major.   Make sure you clean that.   It's the only way to get the Flavor