Sarkis and 
Sudestada are my two favorite BA go-to's.  Whenever I need cheap, tasty, and different my move is Sarkis.  Whenever I need spicy (and I mean bad ranking in guiaoleo because Argie's can't handle it spicy) I go to Sudestada.  Definitely give both these a try if you haven't yet and be sure to order the following items:
 
Sarkis - falafel and chicken or lamb fierro/kebab/whatever it's called COMPLETO with the yogurt on the side.  The yogurt is amazing, thick, doesn't exist in BA style so it's a must on the completo, but you need to ask for it "a parte" or you'll get screwed by an excess of it drenching everything.  
Sudestada - the jalapeno cocktail, the grilled rabbit, and the curry special.  Ask for extra picante if you like spicy because it's LEGIT, almost borderline too spicy for me, but a welcome change from typical argie fare where carne picante empanadas may as well be dulce in my opinion.
Both places are winners and not to be missed.
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| Chicken kebab completo  | 
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| Spanakopita | 
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| Falafel | 
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| Yogurt on the side | 
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| Fish balls - AMAZING | 
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| Grilled Rabbit | 
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| Green curry chicken |