A current example would be "BAD". There is the normal meaning and the slang meaning of "good" (sometimes pronounced baad for emphasis). Although words in which the antithetical definitions are listed in common dictionaries are preferable, well-known slang examples are also acceptable.

• Anabasis: -- A military advance vs. A military retreat
• Anon : -- Immediately [Archaic] or soon vs. Later
• Anxious: -- Full of mental distress because of apprehension of danger or misfortune [in effect, seeking to avoid] (We were anxious about the nearby gunshots.) vs. Eager or looking forward to (Until you returned, I was anxious to see you.)
• Apparent: -- Not clear or certain (For now, he is the apparent winner of the contest.) vs. Obvious (The solution to the problem was apparent to all.)
• Assume: -- To actually have (To assume office) vs. To pretend to have (To assume an air of confidence)
• Avocation: -- A hobby vs. a regular occupation [and one could say it's a triple antagonym if you agree that the archaic meaning of "a distraction" is the opposite of working (even at a hobby) and if you agree that the obsolete meaning of "a calling away" takes you away from (the opposite of participating in) your hobbies, work, and even your distractions!]
• Awful: -- Extremely unpleasant, ugly vs. Awe-inspiring [typically, a feeling of admiration]
• Bound: -- Moving ("I was bound for Chicago") vs. Unable to move ("I was bound to a post", or less literally, "I was bound to my desk")
• Bull: -- A solemn edict or mandate vs. Nonsense or worthless information
• Chuff: -- Elated vs. Unhappy
• Cite, Citation: -- For doing good (such as military gallantry) vs. for doing bad (such as from a traffic policeman)
• Cleave: -- To adhere tightly vs. To cut apart
• Cool: -- positive sense (cool web-sites) vs. negative sense(cool reception).
• Comprise: -- To contain entirely vs. To be included in ("The United States comprises 50 states"; "The 50 states comprise the United States") [Some will argue with both uses, including me; however, both uses have become commonplace and some sources list both without comment.]
• Counterfeit: -- [Archaic] a legitimate copy vs. a copy meant to deceive
• Cut: -- get in (as in line or queue) vs. get out (as in a school class)
• Dust: -- To remove dust -- vs. To apply dust (as in fingerprinting)
• Effectively: -- in effect (doing the equivalent of the action but not the real thing) vs. with effect (doing the action and doing it well) [Contrast "he is effectively lying" (colloquial?) with "he is lying effectively"]
• Enjoin: -- To order someone to do something vs. To stop someone from doing something [such as in law by an injunction]
• Fast: -- Moving rapidly vs. Unable to move ("I was held fast to my bed.")
• Fearful: -- Causing fear vs. Being afraid
• Goods: -- [Slang] good things vs. bad things ("I have the goods from the warehouse robbery, but I'm worried the police have the goods on me.")
• Hysterical: -- Being overwhelmed with fear [in some cases] vs. Being funny
• Incorporate: -- When a village is incorporated, it is formed, but when it is incorporated into a city, the village is destroyed
• Inflammable [a pseudo-antagonym!]: -- Burns easily vs. [the incorrect assumption by many that the prefix in- makes it mean:] Does not burn [Only the first definition is correct; the risk of confusion has removed this word from gasoline trucks!]
• Last: -- Just prior vs. final (My last book will be my last publication)
• Lease, Let, Rent: -- [in essence] To loan out for money vs. To "borrow" for money
• Left: -- To remain vs. to have gone (Of all who came, only Fred's left. [Does it mean he's the only one who still remains or that he's the first to depart?])
• Let: -- [Archaic] To hinder vs. To allow
• License: -- Liberty or permission to do something vs. Undue or excessive freedom or liberty
• Literally: Precisely vs. often corruptly used to mean "figuratively" (As in: "There were literally millions of people at that party."). Our correspondent writes: Many people think this is an error, albeit a common one; but I think "Literally millions of people" isn't so much error as a form of hyperbole; the trouble is that the literal meaning of "literally" is, among other things, "not hyperbolically."
• Moot: -- [a slight stretch here] A moot point is one that is debatable, yet is also of no significance or has been previously decided, so why debate it?
• Oversight: -- Watchful and responsible care vs. An omission or error due to carelessness
• Peruse: -- Read in a casual way, skim (To peruse the Sunday paper) vs. to read with great attention to detail or to study carefully (To peruse a report on financial conditions).
• Policy: -- Required activity without exception (University policy) vs. An optional course of action (our government's policy regarding the economy)
• Practiced: -- Experienced, expert (I am practiced in my work) vs. Inexperienced effort (The child practiced coloring.)
• Prescribe: -- To lay down a rule vs. To become unenforceable
• Quite: -- Completely vs. Not completely (e.g., quite empty [totally empty]; quite full [not completely full, just nearly so])
• Ravel: -- to disentangle or unravel vs. to tangle or entangle
• Recover: -- hide away (cover again) vs. bring out [hyphenated] (The dinosaur bones were exposed by the flood but then re-covered with dirt, hiding them again; centuries later, the paleontologists recovered them by removing the dirt.)
• Release: -- let go vs. hold on (lease the property again) [hyphenated as re-lease]
• Replace: -- Take away (replace the worn carpet) vs. Put back (replace the papers in the file)
• Repress: -- hold back vs. put forth (press again) [hyphenated]
• Reprove: -- rebuke (reprove a colleague's work) vs. support (re-prove a scientist's theory)
• Reside: -- to stay put vs. [Slang] to change places (change teams) [hyphenated as re-side] [N.B.: -- This is also a heteronym!]
• Resign: -- to quit a contract vs. to sign the contract again [hyphenated as re-sign] [N.B.: -- This is also a heteronym!]
• Restive: -- refusing to move (forward) (a restive horse) vs. Restless (moving around)
• Restore -- [in the following use]: The painting was said to be a fake, so the museum re-stored it in the warehouse. When it was later found to be real, the museum restored it to its place in the gallery.
• Riot: -- Violent disorder vs. Revelry (Consider what is meant when one says, "It was a riot!")
• Rival: -- An opponent vs. (Archaic) A companion or associate
• Rock: -- disturb (rock the boat) vs. pacify (rock the baby's crib)
• Root: -- To establish (The seed took root.) vs. To remove entirely (usually used with "out", e.g., to root out dissenters)
• Sanction -- : Support for an action (They sanctioned our efforts.) vs. A penalty for an action (The Congressman was sanctioned for inappropriate behavior.)
• Sanguine: -- (Now poetic) Causing or delighting in bloodshed [according to contributor, also describes a person worked up into a bloody rage] vs. A person hopeful or confident of success [essentially someone calm about something]
• Screwed: -- [Slang, vulgar] Had a good experience (We screwed around all night.) vs. To have a bad experience (I was screwed by that cheater.)
• Secreted: -- Having put out, released vs. Placed out of sight [N.B.: -- This word is also a heteronym!]
• Shank: -- (Informal) The early part of a period of time (It was just the shank of the evening when the party began.) vs. (Informal) The latter part of a period of time (It was the shank of the evening when the party ended.)
• Shop: -- To search with the intent to buy ("I shopped for a book at several stores.") vs. To search with the intent to sell ("I shopped my manuscript to several publishers.")
• Sick: -- unpleasant (A sick joke) vs. wonderful (Slang: That sportscar is really sick!)
• Skin: -- to cover with a skin vs. to remove outer covering or skin
• Strike out: -- An ending, as in "The batter struck out." vs. A beginning, as in "I thought it was time to strike out on my own." Also, a strike -- in bowling occurs when there is complete contact between ball and wood (of the pins), whereas a strike -- in baseball occurs when there is complete absence of contact between ball and wood (of the bat).
• Terrific: -- (Informal) Extraordinarily good vs. Causing terror

• Could care less: -- (Used as if it were synonymous with "could not care less.") One has no interest at all
• Like never before: -- totally amateurish vs. with great skill (She's dancing like she's never danced before.)
• Look out for: -- see Watch out for
• Take care of: -- Look out for and nurture vs. get rid of or kill
• Near miss: -- A hit close enough to achieve the effect vs. narrowly falling short of the objective
• Watch out for: -- A positive statement meaning try to find or partake of vs. A negative statement meaning avoid (Watch out for this movie.)

• Fat chance; slim chance: -- (Both mean "not too likely")
• Cool; hot: -- (Both mean wonderful [Slang], e.g., when applied to a car)

• Biweekly (Biyearly): -- twice a week (year) vs. every two weeks (years) (the former is used "loosely")
• Daily: -- 5 days a week vs. 6 days a week vs. 7 days a week (for example, the "daily" newspaper)

• Seeded: -- Clouds are seeded (something is added) to produce rain vs. grapes which are seeded (the seeds are removed). Also, if one removes the seeds from cherries they are pitted but if one sows grass seed in the yard, the yard is seeded.
• Shelled: -- Having the shell removed (shelled pecans) vs. Enclosed in a shell (tiny, shelled marine animals)
• Skinned: -- See skin, above.