There are no words that have double-x in them.
Words with double t's:atticattachattainattireattitudebatterybettingbrittlebarrettebuttressbetterbitterbottlebutterbuttonblottercattlecassettecommitteecluttercottoncuttingdittodiskettedinetteetiquetteflutterfritterfatterfetteredfittedglittergutterhitterhotterjitterykettleknittedknottedlittlelotterylettermattermattednettedotterpatternpattypattedpottingpotteryputterpettedrattlesettlestutterspattersputterspittingsplittingspottedswattedslottedscattertattleutterlyvettedwittedkittenlitterbatteredpatternsbetterbottompermitted
Examples of words with double consonants:abbreviationacceptallureassumeaffableaggressiveanniversaryballetbarrettebubblebabblebobblecuddlecattlecrabbychubbycoffeecellarcollarcallousdollardilldimmerellipseflattenflabbyfloppyfoggyflutterfrazzleflatterflammablegabbyhappyhasslehammerissueillinnjollylullladderletterlattermaggotmuzzleoccupyoffoddpaddlepuzzlepuddleparrotpuffquillquellrallyreallyrapportsummerslobbersaddlesettlesuddenshippedsnappedtabbytrippedtaffytoggleuddervolleyvalleywhiffwafflewrappedyellowyuccazappedzipper
Some words with a double 'h' are:bathhousefishhookhitchhikerhighhandedroughhewnroughhouseshhwithhold
Some double N words are:announceannoyannexanniversaryantennaannualbandannabannerbanningbeginningbonnetbunnycanneryconnectcannibalcanningcannoncannulacayennechannelconnoteconnoisseurcunningdinnerdisconnectevennessfanningfennelflannelfunnelfunnygrannygrinninghennainninnateinnerinningjuliennekennelmannersmanningmannishmayonnaisenannyninnynunneryopennesspanningpennantpennypinnaclepinningplanningquestionnairereconnectroadrunnerrunningrunnyscanningskinnysonnetspinningstunningsunnytanningtennistunneltyrannyuncannyunnerveunnoticedwinningwinnowzinnia
Aardvark and eel are words. They begin with double letters.
words likeflammablerummagelummoxbummergrammarimmediateimmenseimmigrantimmortalimmobileimminentimmuneimmortalimmodestimmobilerecommendcommentsummerhammertrimmerdrummerstammersimmershimmerglimmer
Words with two double Es is beekeeper (and variants), peewee, and teepee.
Some words that have double Es are:agreeamputeeapogeebansheebeebeechbeefbeenbeepbeerbeetbeetlebeseechbetweenbleedbooteebreechbreedbreezebungeecanteencareencareercheekcheepcheercheesecheetahchickadeecoffeecouleecreelcreepdecreedeeddeemdeepdeerdegreediscreetemceeengineerexceedfeefeeblefeedfeelfeetfianceefiligreefleefleecefleetfreefreezegeekgeesegenteelgleegoateegreedygreengreetheedheeljamboreejeepjeerjubileekeelkeenkeepkneeleeleechleekleerleveelicheemanateemarqueemeekmeetmeleeneeneedneedlenegligeeoverseeparakeetpedigreepeepeekpeelpeeppeerpeevepeeweepreemiepreemptpreenproceedprotegeepureequeenqueerreedreefreeferreekreelrefereerefugeerupeesateenscreescreechscreenseeseedseekseemseenseepseerseesawseethesheensheepsheersheetskeetsleeksleepsleetsleevesneersneezespeechspeedspleenspreesqueegeesqueezesteedsteelsteepsteeplesteersteeragestreetsucceedsweepsweetteeteemteenteethteethetepeetheethreetoffeetoupeetreetureentweedtweettweezerveejayveerveneerweeweedweekweenweepweevilwheewheedlewheelwheezeyippee
Some words that have UU in them are:continuummuumuuresiduumvacuum
Here is list of words with a double 'V'chivviedchivvieschivvychivvyingcivviescivvydivvieddivviesdivvydivvyingflivverflivversnavviesnavvyrevvedrevvingsavviedsavviersavviessavviestsavvysavvyingskivviedskivviesskivvyskivvyingSome of these words are rarely used, or are only used in limited circumstances.
arrowbarrowcarryearringharriedjarredmarrownarrownarratornarratenarrativeparrotquarrystarrytarry