Everyone has staples they turn to, especially when it comes to t-shirts. American Apparel is mine. Issues with the previous guy in charge now resolved, they offer good t-shirts at a decent price.
Their tri-blend short sleeve t-shirt is one with a nice slim shape to it, yet thankfully isn't as tight as the 'muscle hugging' varieties out there. It has a high neckline too: one that's high enough just to be seen when wearing a round-neck jumper and doesn't crease or ruffle.
Perhaps not a t-shirt you can wear for every occasion - it wouldn't pass the Sunspel test of looking good with shoes, but then again, few do - it's definitely one that can be worn with pretty much anything else.
American Apparel are always offering 10-15% discounts when you buy online; so go on, fill that cupboard!