Neckwear
Bowtie
Probably the thing to wear with a classic tux. Bow ties come in several colors besides basic black --- white is reserved for super-formal events, and colored bow ties are suitable for any occasion. You can match the wedding colors, but basic black is far classier. The black bow tie is standard, other options are offered at an additional cost.
Ascot tie
This wide, formal tie is usually patterned, folded over, and fastened with a stickpin or tie tack. Usually reserved for ultra-formal daytime weddings and worn with a cutaway coat and striped gray trousers.
Bolo tie
If you're having a Western-theme wedding.
Euro tie
This is a hybrid between an ascot tie and a regular, run-of-the-mill necktie. It's a long, square-bottomed tie knotted at the neck and worn with a wing collar or spread collar shirt. The Euro offers a more formal look that's not as all-out as an ascot.
Necktie
They're also called four-in-hands and are perfect for more casual -- yet still elegant -- wedding looks.