I don't know your vocal range, but I love it when people sing little-known songs from popular artists. For example, Donald Lawrence's "Usher Me" and "Lord, I Try" (I think both of those were on the
Go Get Your Life Back CD) are both great songs for a solo, and they weren't released as singles, so a lot of people don't know them. On a side note, "Usher Me" is a great P&W song, as well.
I also think you can't go wrong with an old hymn. Even if you do sing a more common one, if you make it your own, and kill it, you can kinda make it your signature... you know, the song people WANT to hear you sing whenever you take the mic.
In Atlanta, I think everyone pretty much agrees on who the greatest male vocalist is... he is young and trendy, and can outsing anyone I know, nationally or locally. But, his signature song is "Tis So Sweet." The first time I heard him sing it, when I saw him telling the organist that's what he was gonna sing, I was like

*sigh*... but he KILLED IT.... and to be honest, I don't want to ever hear anyone else sing that song if it ain't him!
Same goes for a well-known female vocalist in Atlanta... her signature song is "Let Jesus In" (though I'm not sure that's the name of it).... Anyway, I brought her in to sing that song once, and she told me that she regrets ever singing it because now, that's the only song anyone in Atlanta will ever let her sing.
I guess what I'm saying is that you can take a simple hymn, make it YOURS, and be set... whether it's a "creative" song or not...