The show of force - and the Palestinian Authority's persistent failure to stop people from crossing Gaza's border with Egypt - underscored Palestinian leader Mahmoud Abbas' trouble in asserting control.
Abbas meanwhile pledged to seal the chaotic border within "two or three days", but previous deadlines passed without change.
With elections approaching in January, Hamas and Abbas' Fatah faction are locked in an increasingly bitter power struggle and each is trying to use the pullout for political gain.
Abbas is under heavy international pressure to disarm resistance fighters, a call reiterated by Israeli Prime Minister Ariel Sharon in a speech to the United Nations on Thursday.
The two leaders are scheduled to meet early next month.
Hamas rejects Abbas' pleas to disarm, saying its attacks drove Israel out of Gaza and that armed resistance will continue. One Hamas commander, Fathi Hamad, said that instead of disarming, Hamas will build up its arms. "We will increase our production capacity and the purchase of weapons," he said.
"We will increase our production capacity and the purchase of weapons"
Hamas and Fatah have held competing victory celebrations since Israel completed its Gaza pullout on Monday, and Hamas has had far bigger turnouts.
Some 10,000 people joined Friday's rally in the ruins of Neve Dekalim, which weeks ago was the largest Israeli settlement in Gaza. People waved green Hamas flags, held posters of Hamas' founder, Shaikh Ahmed Yassin, who was killed in an Israeli missile strike last year, and burned plastic foam models of Jewish settlements.
Standing in columns and clad in camouflage, the Hamas fighters resembled a private army. They fired machine guns into the air, and Hamas vehicles displaying homemade rockets and grenade launchers on their roofs drove over an Israeli flag.
Ismail Haniyeh, a Hamas leader, mocked Sharon's latest call for Abbas to crack down. "We tell Sharon: Fool, you are asking the Palestinian Authority to do something you have failed to do with all your might," he said.
Earlier on Friday, hundreds of masked Hamas fighters in military-style fatigues paraded through the abandoned settlement of Netzarim.