For 5E, it has to be the monk.
I really like the class concept, and I know that it's fairly balanced around the concept of having high Dex and Wisdom at the expense of Strength, but it just feels wrong to punch for 1d8+5 when I have a Strength of 8. Monks are supposed to be the physically strongest class, not the weakest.
Bard. Because every game I've joined has already had one.