It ain't always great being a giant ... just ask 7'6" NBA draft prospect Tacko Fall ... who's telling TMZ Sports what sucks most about being incredibly tall!!

The ex-UCF Knights star was towering through LAX on Thursday ... when he gave us the lowdown on the pros and cons of being one of the tallest people on the planet.

Tacko says it comes in handy at the grocery store whenever he needs to reach the top shelves and "look over everything" ... but when it comes to bathing, it really stinks ... 'cause he's taller than the shower!!