Or:
Taiyō & Tsuki (sun & moon)
Yoake & Yūgure (dawn & dusk)
Kuro & Shiro (black & white)
Hidari & Migi (left & right)
Naibu & Soto (inside & outside)
Hai & Nashi (yes & no)
Meido & Yami (lightness & darkness)
Hikari & Kurai (light & dark)
Uso & Shinjitsu (the lie & the truth) (Hmm... where did I hear this before...)
Josei & Otoko (woman & man)
Shōnen & On'nanoko/Shōjo (boy & girl)
Kotonaru & Onaji (different & the same)
Ai & Kirai (love & hate)
Amai & Nigai (sweet & bitter)
Suppai & Shio (sour & salt)
Amai & Shio (sweet & salt)
Satō & Shio (sugar & salt)
Natsu & Fuyu (summer & winter)
Natsutaiyō & Fuyutsuki (summer sun & winter moon) (actually, it has to be Natsu no taiyō and Fuyu no Tsuki, but in names it's nicer to forget the no's.)
Haru & Aki (spring & autumn)
Haruhi & Akitsuki (spring sun & autumn moon)
Haruka & Amari (much & not much)
I think the last pair are the nicest ones! I can also give you the kana/kanji of the names if you want so...