Here is a list of extensions that could be excluded from being scanned on the average system. Feel free to add your own.
aac, acs, adc, adm, ai, am, art, avi, awe, bat, bin, bkf, bmp, cab, cat, cfg, chm, class, clx, cmd, cnt, cnv, com, config, cpl, cpp, cs, csf, css, cur, cw, dic, dll, dlm, dotx, env, eps, evt, evtx, exe, flt, fon, gif, h, hhk, hiv, hlp, hxs, hxw, hyp, icc, icm, ico, idx, inf, ini, iso, its, jar, jpeg, jpg, js, jse, lex, lib, liveupdate, lnk, lxa, m4a, m4p, m4v, mda, mdf, mid, mof, mov, mp3, mp4, mpeg, mpg, msc, msi, msp, mst, ngr, ocx, ogg, olb, pf, pfb, pfm, pnf, png, ps1, psd, psp, py, pyw, query, rll, rm, rmm, rmx, rp, rpm, rpv, rts, sdb, smi, spd, swp, sys, theme, tif, tiff, toc, ttc, ttf, vb, vbe, vbn, vbs, vdf, vhd, vmdk, vsd, wav, wma, wmb, wmdb, wmv, wpc, wsf, wsh, xaml, xdr, xml