One or two letters words: 2d, 3d, A, AA?, Ab, Ac?, Ad?, Ag?, Am, An?, Ar?, As?, At?, AU, B, Be, C, D, DC?, E, F, G, Go, H, Hg, I, J, K, L, M, MM, N, Nu, O, P, Q, R, S, SF, SI, SS, T, TS, U, UC, US, V, W, X, Xe, Y, Yb?, Yd?, Z, Zn?, Zr?
Three letters words: AaA, ABC, Act?, AdA, Ada, Adz?, AFC?, Aga?, Age?, AGM?, AGR?, Aid?, Ail?, Aim?, Air, Aka?, Ale, All?, Amp?, ANC?, And?, Ant, Any?, AOB?, AOL, Ape, Apr?, Apt?, Arc?, Ark, Arm?, Art, Ash, Ask?, Asp?, Ass?, Aug?, Auk?, Aux?, Ave?, Awe?, Awk, Awl?, Axe?, Aye?, BBC, BLM, BMW, BPM, Bps?, BSD, Bar, Bay, Bit, Bse, CDU, CEO, CPU, CSU, Car, Cow, DES, DIN, DNA, Dna, Eye, FDP, Fax, GDP, GNU, GPL, GPS, GUI, Gay, Gnu, GoD, God, Gun, Hex, IAm, IBM, IMR, IOC, IRC, ISO, ITU, Inn, Ion, JFK, LA2, LMS, LSD, Law, Leo, MD5, MIT, MTV, N64, NFL, NMD, NWA, NYC, NnN, OSI, Out, PCM, PDA, PDS, PGP, PHP, RAM, RFC, RSA, Rap, Rpm, SGI, SPD, STG, SUV, SeT, Sea, Sed, Set, Sex, Sun, TeX, Tea, Tin, UCB, UPU, URL, UuU, War, XML, XfL, Y2K, Yak?, Yam?, Yap?, Yaw?, Yen?, Yes?, Yet?, Yew?, YHA?, Yin?, Yob?, You?, YTS?, Yuk?, Zap?, Zen, Zip?, Zit?, Zoo?, ZzZ
Four letter words: 1040, 1909, 1952, 1964, 1977, 1984, 1999, 2000, 2001, ABBA, AbeL, Abel, Abet?, Able?, Acid, Acme?, Acne?, Acre, Adze?, Aeon, Afar?, Agar?, Agog?, Ague?, Ahoy?, Aide?,
Airy?, Ajar?, Akin?, Alas?, Alga,Ally?, Alms?, Aloe, Alto?, Alum?, Amen?, Amid?, Amir, Amok?, Anal?, Anew?, Apex?, Arab, Arch?, Area, Aria?, Arid?, Arms?, Army, Arse?, Asap?, Asia, Atom, Audi, Aunt?, Aura?, Auto?, Aver?, Aves, Avid?, Avow?, Awry?, Axis?, Axle?, B-52, Bach, BalL, Bank, Bass, Bead, Beer, Bell, Bird, Bonn, Book, Calf, Chad, City, CodE, Code, Cuba, Data, Dock, Dune, Enya, Euro, Fear, FiLm, Fiji, Film, Fish, Flub, FoMa, Food, Ford, Free, Geek, Gobi, Gods, Gold, Guam, Gulf, HerA, Hera, Herb, Homo, Hurd, Inch, Iowa, Iran, Iraq, Iron, Isms, Java, Jazz, Jeep, Jews, Jlnd, JudO, Judo, Jung, King, Koto, Lake, Laos, Lead, Love, Mali, Mark, Mars, Mass, Math, MeaN, Meat, Mile, Mint, MoDe, Mode, Mojo, Mole, Moot, MppC, Nazi, Neon, Neva, Nile, Niue, Oboe, Ohio, Opel, Oslo, PaGe, Perl, Pipe, Play, Pope, Riga, RinG, Ring, Risk, Rome, Ruby, Saab, Sage, Seal, Seat, Sect, Sets, Ship, SiVa, Siam, Smog, Sony, Star, Stop, Tone, Tort, Troy, Unit, Unix, Urea, Uric, UtaH, Utah, Veal, Wiki, Wine, WolF?, Word, Yang?, Yank?, Yard, Yarn?, Yawn?, Year, Yell?, Yelp?, Yoga, Yoke?, Yolk?, Yore?, York, Your?, Yowl?, Yuan?, Yuck?, YWCA?, Zeal?, Zero, Zest?, ZeuS, Zeus, Zinc, Zing?, Zits?, Zone?, Zoom?, Zope, Zork, Zulu
Four letter apparent acronyms? that _definitely should_ be in Wikipedia:
ACAS?, AIDS, AMEX?, ANSI, CFAF, ETSI, HTML, HTTP, IEEE, IETF, IHES, IKEA, INRI, IRIX, ISOC, LALR, LOGO, MIME, MPPC, NATO, OPEC, POP3, SEGA, UNIX, USSR, YMCA,