The Skinny Top
As a general rule the most universally flattering top is a V-neck, 3/4 sleeve, fine fabric with a heavy weight to it, that skims your figure and ends about to the top of your hip.
Another slimming suggestion is that the wider you are in your shoulders or bust, the less fabric you should have in your neckline, try not to crop above your hips, and choose a heavy gauge fabric to glide over your body, rather than a thin fabric that may fall into folds.
Here is some slimming and body balancing guidelines on the rest of the necklines out there:
A Strapless top -
Great if you do not need a lot of support from a bra and they still defy gravity, also it can make your arms look good, taking the attention off of them leaving them bare and streamlined. Wide shoulders can hold this well.
Flattering on most figures with slimming effects. A deep v-neck can minimize a large bust.
Spaghetti-Strap Tank -
If you have great arms, and an average to smaller bust, this can make the eye slim you with its up and down effect.
Mandarin Collars -
Petite and small shoulders look great in these.
Collared Shirt -
Most figures look great in this, especially when the collar is popped up to elongate the neck and shadow the jawline nicely. Go bigger on collar with a bigger bust.
Slim shoulders and small upper bodies look lovely in this style, it can help to offset wider hips.
Is lovely on slender upper bodies with a smaller bust. Adds volume to the upper body, and can help to balance a heavy lower body.
Gives a lovely roundness to the chest area, and works for all Bust sizes.
A long neck can pull this off well, can hide a thick neck.
Round T-shirt Neck-
Can be worn by all, does not amplify or reduce the appearance of the bust, keep it skimming the body in a heavy gauge fabric. Stay away from the ultra thin t's out there.
Flattering yourself with the right neckline and balance on your body,
will attract and get the attention your face deserves.