To some extent, yes. In the late eighteenth century, Polish revolutionary Tadeusz Kościuszko organized a peasant corps called the "Kosynierzy," roughly translated as "the Scythers." Due to shortage of war material, they were armed with modified scythes. For the most part, they were utilized as a kind of peace-keeping militia. However, they also participated in battle as auxiliary units during the 1794 insurrection against Catherine II's (of Russia) Second Partition of Poland. That said, practically, they were of secondary military importance to regular armed troops. Psychologically, their organization sought to create a powerful vision of a more egalitarian, equal, enlightened Polish state in which peasants self-identified as citizens, not just a toiling underclass.

Mariusz Markiewicz, Historia Polski, 1492–1795 (Kraków: Wydawnictwo Literackie, 2002); Jerzy Topolski, Polska w Czasach Nowożytynych (1501-1795) (Poznań: Wydawnictwo Naukowe Uniwersytetu Adama Mickiewicza, 1999); Włodzimierz Suleja, Kosynierzy i strzelcy: rzecz o irredencie, (Wrocław: Wydawnictwo Dolnośląskie, 1997)

EDIT: Specific dates, punctuation, bibliography, obsessive-compulsive stylistic corrections.

The Classical Romans under Trajan really came a cropper of the Dacian Falx which was a modified scythe ('Flax represents the Latin word for scythe or sickle' A. D. Alexandrescu, in Dacia 1980). It was so effective that it was one of the rare occasions the Roman army was forced to modify their armor on campaign to include thicker armor for their arms as they Dacians were so effective at using the hooked blade of the Falx to get around the roman shields and take out limbs with it. In comparison, even the Parthian's iconic arrow barrages were of little concerns as Trajan now had ‘experienced soldiers who were not afraid by the enemy’s arrows after facing the horrific wounds made by the curved swords (falces) of the Dacians' (Marcus Corneli Frontonis)

The weapon is still viewed as a cultural icon and source for nationalistic pride in Romania, the site of the ancient Dacian homeland: check out these amazing images of the weapon and of monuments dedicated here: http://www.tumblr.com/search/dacian%20falx

And I would recomend this article that covers how this and other similar Dacian weapons evolved and had such a impact in their disputes with Rome: http://www.academia.edu/1143674/Thracian_sica_and_Dacian_falx._The_history_of_a_national_weapon

Edit: here's another interesting source; Tried finding some good videos of it featured in the new Total War Rome series but they got nerfed on all accounts (poor form Sega) but in looking for it found a apt and interesting video that covers exactly how fierce this weapon was: https://www.youtube.com/watch?v=IB8EHonhovg

Okinawan MA trains in the sickle.

Peasants forbidden to own formal weapons made their own fighting forms w/ what they had lying around: Tonfa, Sickle, etc.

Also bladed weapons work best in certain environments, in others not so well.

For e.g. Guhrkas specialize in the Kukri, which is very, very short. Yet in the dark, close quarters, in the jungle, very advantageous. Even against longer samurai swords like happened in Burma.

Falxes, a weapon of Dacian origin, are often described as being scythe-like and are probably the closest you might be able to find. It does not curve as far forward as the kind you generally see in videogames etc (I assume you mean more close the classic grim reaper design). It apparently was effective enough that legionaries modified their armor during the Dacian wars to help prevent the falx from being able to circumvent their shield and hit their helmet, upper body, etc. There are a number of pole arms (namely bills) that are similar in concept, but differ in design from the classic because of the length of the forward curve relative to the length of the blade itself. Their usage tend to be more similar to classic spears with a cutting edge.

Sickles seem to have a few examples in use in Japan and the far east. Note the Kama. http://en.wikipedia.org/wiki/Kama_(weapon)

I'm sure there are plenty more examples.

Speaking of using farm implements in battle- I could think of a more recent event involving a plow coulter; I present to you, the Honey War.

http://en.wikipedia.org/wiki/Honey_War#The_.22War.22

According to one description about the Iowans:[4] in the ranks were to be found men armed with blunderbusses, flintlocks, and quaint old ancestral swords that had probably adorned the walls for many generations. One private carried a plow coulter over his shoulder by means of a log chain, another had an old-fashioned sausage stuffer for a weapon, while a third shouldered a sheet iron sword about six feet long.

A Khopesh is a related, albeit distantly, weapon to the Falx & Sickle as well. It derives from a far older era and fell out of common use in North African and Middle Eastern countries before 1,000 BCE. It is a crescent bladed sickle-sword that excels at disarming and stabbing in close quarters.

This is an iconic weapon of the Ancient Egyptians.