My mother's tongue is hungarian, so it isn't difficult for me :). But I am aware of it: Hungarian is one of the most difficult languages of the world. I can speak Hungarian easily, but it's grammar is really hard.
We have a lot of causes (I think 35).
Our language is an agglutinative language, so we use inflections (for (almost) everything) (I think the best example is the word "fiaiéi". It's forming the next way: first stop is fiú (boy), second stop is fia (his/her son; it's an irregular possessive case; the word "son" in hungarian is "fiúgyermek", but this word isn't very used), third stop is fiai (his/her sons; "-i" is the inflection of plural), forth stop is fiaié (his/her sons'), and the final stop is fiaiéi (his/her sons' (plural object))).
We also have extremely long words, such as "megszentségteleníthetetlenségeskedéseitekért" (it's forming the next way: "meg-" is verb prefix (in this case, it means "completed"), "szent" means holy (the word root), "-ség" is like English "-ness", as in "holiness", "-t(e)len" variant of "-tlen" (noun suffix expressing the lack of something, like English "-less", as in "useless"), "-ít" is a constitutes a transitive verb from an adjective, "-het" is expresses possibility (somewhat similar to the English auxiliaries "may" or "can"), "-(e)tlen" is another variant of "-tlen", "-ség" (it mean's see above), "-es" is constitutes an adjective from a noun (like English "-y" as in "witty"), "-ked" is attached to an adjective (e.g. "strong"; produces the verb "to pretend to be (strong)") "-és" is constitutes a noun from a verb (there are various ways this is done in English, e.g. "-ance" in "acceptance"), "-eitek" is plural possessive suffix (second person plural (e.g. "apple" -> "your apples", where "your" refers to multiple people)) and "-ért" is approximately translates to "because of" (or in this case simply "for"). So this extremely long word means: "for your [plural] repeated pretending to be undesecratable" (we also have long words, such as "töredezettségmentesítőtleníttethetetlenségtelenítőtlenkedhetnétek" (it means "you [plural] could constantly mention the lack [of a thing] that makes it impossible to make someone make something defragmenter-free") or "elkelkáposztásítottalanítottátok").
We also have a lot of (used) synonyms (for example, we have 78 synonyms for verb "to move" (and all's meanings are a little bit other): halad, jár, megy, dülöngél, lépdel, botorkál, kódorog, sétál, andalog, rohan, csörtet, üget, lohol, fut, átvág, vágtat, tipeg, libeg, biceg, poroszkál, vágtázik, somfordál, bóklászik, szedi a lábát, kitér, elszökken, betér, botladozik, őgyeleg (old word, we usually don't use it), slattyog (old old word, we usually don't use it) bandukol (old word, we usually don't use it), lófrál, szalad, vánszorog, kószál, kullog, baktat, koslat, kaptat, császkál, totyog, suhan, robog, rohan, kocog, cselleng, csatangol, beslisszol, elinal, elillan, bitangol, lopakodik, sompolyog, lapul, elkotródik, settenkedik, sündörög, eltérül, elódalog, kóborol, lézeng, ődöng (old word, we usually don't use it), csavarog, lődörög, elvándorol, tekereg, kóvályog, ténfereg, özönlik, tódul, vonul, hömpölyög, ömlik, surran, oson, lépeget, mozog, mozgolódik).
We have a lot of dialects in Hungary (and we usually understand all of it, but sometimes it is complicated). The understood difficulty is a result of hungarian word order in the hungarian sentences. As a matter of fact, in the hungarian language there really isn't any kind of attached word order (but every sentence's mean is a bit other). For a hungarian person (who's mother's tongue is hungarian) this doesn't constitute any kind of problem, but for an other person (who's mother's tongue isn't hungarian) it means incredible difficulties.
Our spelling is also complicated. We have many irregular causes (almost everywhere) and our accent is also very hard (for a not-hungarian), because we use many rules for a hungarian word's accent (and we have many-many irregular words from this grammatical category too). The word's irregularity is the hardest in inflections (for me too: it's very hard for me to learn it at school, when we learned irregular conjugations). Our phonetics is also difficult. And we also have slang.
I can keep on this assignment, but it would be a very long comment. So everyone, believe me: Hungarian is possibly not the most difficult language of the world, but it is very difficult (but not for me, because I'm hungarian :D).