Don't Leave me This Way - Harold Melvin & the Blue Notes - one of my personal favourites, especially the full length version.

Went down a storm at a Wedding in Warrington this year, but not as a slowly!
My top ten 'safe' suggestion in no particular order -
Amazed - Lonestar
From This Moment On - Sania Twain
Truly Madly Deeply - Savage Garden
Unforgettable - Natalie & Nat King Cole
Everything I Do - Bryan Adams
I Don't Want to Miss A Thing - Aerosmith
Let's Stay Together - Al Green
Just The Way You Are - Billy Joel
Have I Told You Lately - Van Morrison
What A Wonderful World - Louis Armstrong