For lebanese food: Mounir, Beit Mery. Amazing view and the best food ever (mmmm kebbe nayeh).
and Burj el Hammem, Broummana, very nice setup in the summer and the food is excellent too (I prefer Mounir's though).
French: La Gargote, Broummana. The best steak-au-poivre and salad in the universe. Ideal for a first date. It's a small resto with candles and some nice french music of the good old days.
Italian: Il Giardino, Hotel Al-Bustan, Beit Mery. Pizza with extremely thin crust that you won't forget. The pasta they offer is amazing too (fettucini and co).
After dinner, you can stop at the very cool "Scottish bar" for a drink (in the same hotel). It has an amazing view on Beirut.
For Crepes, "Tonino".
For sandwhiches, Farrouj El Achkar. Sandwhich tawoo' malghoum bel toum :).
Everytime I go back home I go to these restaurants again :-). Checklist.
I sound too "Beit Mery, Broummana
" in this reply but really ma fi mennon hal restaurants.