A list of banned usernames to use in forums and even sites like this one should you wish.
TRUE, FALSE, 101, 111, 400, 401, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 421, 422, 423, 424, 426, 428, 429, 431, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 911, 999, .htaccess, .htpasswd, .well-known, about, About, about-us, abuse, access, account, Account, accounts, Activate, ad, add, Add, admin, Admin, Admin, administration, administrator, Administrator, Administrator, ads, advertise, advertising, aes128-ctr, aes128-gcm, aes192-ctr, aes256-ctr, aes256-gcm, affiliate, affiliates, ajax, alert, alerts, alpha, amp, analytics, api, Api, app, App, apps, Apps, Archive, Archives, asc, assets, atom, auth, Auth, authentication, authorize, autoconfig, autodiscover, avatar, backup, banner, banners, beta, Better, Better, billing, billings, blog, Blog, blogs, board, bookmark, bookmarks, broadcasthost, business, buy, cache, Cache, calendar, campaign, Cancel, captcha, careers, Careers, cart, Cart, cas, categories, category, cdn, cgi, cgi-bin, chacha20-poly1305, change, Changelog, channel, channels, chart, chat, checkout, Checkout, clear, client, close, cms, Codereview, Codereview, com, comment, comments, community, compare, Compare, Compare, compose, config, Config, Configuration, connect, Connect, contact, Contact, contest, cookies, copy, copyright, count, create, Create, crossdomain.xml, css, curve25519-sha256, customer, customers, customize, dashboard, db, deals, debug, delete, Delete, desc, destroy, dev, developer, developers, diffie-hellman-group14-sha1, diffie-hellman-group-exchange-sha256, Direct_Messages, disconnect, discuss, dns, dns0, dns1, dns2, dns3, dns4, docs, documentation, Documentation, domain, download, Download, downloads, Downloads, downvote, draft, drop, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, edit, Edit, editor, email, Email, Employment, enterprise, Enterprise, error, errors, event, events, example, exception, exit, explore, export, extensions, Facebook, family, faq, Faq, faqs, favicon.ico, Favourites, features, feed, Feed, feedback, Feedback, feeds, Feeds, file, files, filter, Fleet, Fleets, follow, Follow, follower, followers, Followers, following, Following, fonts, forgot, forgotpassword, forgot-password, form, forms, forum, forums, friend, Friend, friends, Friends, ftp, get, Gist, git, go, group, Group, groups, Groups, guest, guidelines, guides, head, header, help, Help, hide, hmac-sha, hmac-sha1, hmac-sha1-etm, hmac-sha2-256, hmac-sha2-256-etm, hmac-sha2-512, hmac-sha2-512-etm, home, Home, host, Host, hosting, Hosting, Hosting, hostmaster, Hostmaster, Hostmaster, htpasswd, http, httpd, https, humans.txt, icons, Idea, Ideas, images, imap, img, import, index, Index, info, Info, Info, insert, investors, invitations, Invitations, invite, Invite, invites, invoice, is, Is, Is, isatap, issues, it, It, It, Job, jobs, Jobs, Jobs, join, js, json, Json, keybase.txt, learn, legal, license, licensing, like, limit, List, Lists, live, load, local, localdomain, localhost, lock, login, Login, logout, Logout, Logs, lost-password, mail, Mail, mail0, mail1, mail2, mail3, mail4, mail5, mail6, mail7, mail8, mail9, mailerdaemon, mailer-daemon, map, Map, Maps, marketing, marketplace, master, me, media, member, members, message, messages, metrics, Mine, mis, Mis, Mis, mobile, moderator, modify, more, mx, my, net, network, new, news, News, newsletter, newsletters, next, nil, nobody, noc, none, noreply, no-reply, notification, notifications, ns, ns0, ns1, ns2, ns3, ns4, ns5, ns6, ns7, ns8, ns9, null, oauth, Oauth, Oauth_Clients, oauth2, offer, offers, Offers, online, openid, Openid, order, Order, orders, Orders, Organizations, Organizations, overview, owner, page, pages, partners, passwd, password, pay, payment, payments, photo, photos, pixel, plans, Plans, plugins, policies, policy, pop, pop3, popular, Popular, portfolio, post, Post, postfix, postmaster, Postmaster, poweruser, preferences, premium, press, previous, pricing, print, privacy, Privacy, privacy-policy, private, prod, product, production, profile, profiles, project, projects, Projects, public, purchase, put, Put, quota, Recruitment, redirect, reduce, refund, refunds, register, Register, registration, remove, Remove, replies, Replies, reply, report, request, request-password, reset, reset-password, response, return, returns, review, reviews, robots.txt, root, Root, Root, rootuser, rsa-sha2-2, rsa-sha2-512, rss, Rss, rules, sales, Sales, save, Save, script, sdk, search, Search, secure, security, Security, select, services, session, sessions, Sessions, settings, Settings, setup, share, shift, shop, Shop, Shop, signin, signup, Signup, Signup, site, sitemap, Sitemap, sites, smtp, sort, source, sql, ssh, ssh-rsa, ssl, Ssl, ssladmin, Ssladmin, Ssladmin, ssladministrator, Ssladministrator, Ssladministrator, sslwebmaster, Sslwebmaster, Sslwebmaster, stage, staging, stat, static, statistics, stats, status, Status, Status, store, Stories, Stories, style, Styleguide, Styleguide, styles, stylesheet, stylesheets, subdomain, subscribe, Subscribe, Subscriptions, sudo, super, superuser, support, Support, survey, sync, sysadmin, Sysadmin, Sysadmin, Sysadministrator, system, Systemadministrator, tablet, tag, tags, team, telnet, terms, Terms, terms-of-use, test, testimonials, theme, themes, today, tools, topic, topics, tour, Tour, Tour, training, translate, translations, Translations, Translations, trending, Trends, trial, Twitter, Twittr, umac-128, umac-128-etm, umac-64, umac-64-etm, undefined, unfollow, Unfollow, unlike, unsubscribe, Unsubscribe, update, Update, upgrade, Url, usenet, user, User, username, users, uucp, var, verify, video, view, void, vote, Weather, webmail, webmaster, Webmaster, website, widget, Widget, widgets, Widgets, wiki, Wiki, Wiki, wpad, write, Ww, www, Www, www1, www2, www3, www4, www-data, Wwww, Xfn, Xml, Xmpp, Yaml, Yml, you, yourname, yourusername, zlib,
Please do let us know if you have more to add.