Sora, I'm confused. Are you asking about songs to walk out to ("First Dance") type music, or reception music in general? Do you want something dark, or happy?
As far as I can say, the songs that have hit me the hardest are some of the classics, and for that very reason.
In My Life, The Beatles
I'll Stand By You, The Pretenders
What a Wonderful World, or A Kiss To Build A Dream On, both by Louis Armstrong
She's Got a Way, Billy Joel
Can't Take My Eyes Off of You, Valli and the 4 Seasons
The Way You Look Tonight, Our Love is Here to Stay, or Fly Me To The Moonall by Sinatra
First Time Ever I Saw Your Face, Roberta Flack
I Can't Help Falling In Love, Elvis
Overjoyed, Stevie Wonder
When I Grow Too Old To Dream by Nat 'King' Cole