The Wheelbarrow is a hand-driven vehicle designed to carry huge loads that would be too difficult for someone to carry by hand, such as dirt and wood.
The Wheelbarrow was a cut easter egg and vehicle which was to be featured in Battlefield 2. It was likely cut early on in development, as the only references to the wheelbarrow as a vehicle are unused spotting sound files, where the character would shout "enemy wheelbarrow spotted!" and then laugh, or pretend to be killed. It is also referenced in the localization files.
PLAYER_SPOTTED_C_enemywbspotted Enemy wheelbarrow spotted!
The wheelbarrow does, however, appear as a static world object.