A nice touch is the double-stitched hem, a detail men often look for.
3 Pc Men 100% Cotton A-Shirt Tank Top Ribbed Undershirt Wife Beater Black White
The slim fit on this one has a subtle taper that looks really put together.
XL CSG Mens T-Shirt 100% Cotton V-Neck Short Sleeve Solid Gray BNWT
With a solid pattern, you get a shirt that works for any occasion.
ARMY SOLID OD GREEN OLIVE DRAB PLAIN MENS ROTHCO T-SHIRT S M L XL 2X 3X 4X
This one is made for men, so the shoulders and chest have a roomier cut.
Rothco Mens Athletic Fit Solid Color MilitaryType T-Shirts Tee
What I like is the way it hangs on men, no weird bunching around the waist.