The forward pounced in the closing minutes, steering David Martin’s cross over the line from a matter of yards to ensure Hatters were victorious.
Both teams picked strong sides for the match, with Jon Shaw and Alex Lawless, who had featured in the 5-0 win over Wrexham last night, starting in the Hatters’ team.
Town also included former Shrewsbury and Aldershot defender Ben Herd at right back, while Jernade Meade, Andy Parry, Alex Lacey and Kane Ferdinand all got valuable minutes against a Gills XI, watched by boss Peter Taylor, who included striker Danny Kedwell.
Anthony Charles put a free header off target from Lawless’ corner early on, while Cullen should have opened the scoring, but arrowed wide from a decent position.
Kedwell came closest for the Gills, hooking marginally over the bar, while Elliot Justham also made a good stop at close range to keep the scores goalless.
Matt Robinson tested Sam Baxter into a sprawling low save and from the corner, Lacey’s free header was blocked.
The visitors took the lead on 22 minutes in style when Kedwell flicked the ball up and over a defender, before burying his low drive past the helpless Justham.
Chances were hard to come by on a bobbly surface, but Robinson again tried his luck from distance, firing a bouncing effort into Baxter’s midriff.
Town levelled in brilliant fashion five minutes before the break when Cullen flicked on and Shaw powered a sensational left-footed volley into the top corner.
Shaw almost had a second when his deflected low drive was kicked off the line by a visiting defender.
Both Lawless and Shaw came off at the break for Zane Banton and David Martin and the hosts moved 2-1 in front shortly afterwards.
A lovely move on the left hand side saw Meade slip Martin in and he reached the by-line before crossing for Ferdinand to slam home from close range.
Two almost became three immediately when Robinson robbed his man of possession and Cullen swivelled, shooting inches over.
Hatters always looked the more likely to score in the second period although were indebted to Charles’ well-timed sliding challenge on Adam Birchall, while Justham palmed a dangerous cross over the top.
A spell of Gills pressure was rewarded though when after Justham made an excellent point blank stop, the rebound was met with a brilliant overhead kick by the impressive Lee, giving Town’s number two no chance.
Parry came off late on for David Viana, and Hatters snatched victory too as once again Meade and Martin combined to great effect with the winger’s low cross scuffed over the line from a yard by Cullen.
Hatters: Elliot Justham, Ben Herd, Alex Lacey, Anthony Charles, Jernade Meade, Matt Robinson, Andy Parry (David Viana 85), Kane Ferdinand, Alex Lawless (David Martin 46), Jon Shaw (Zane Banton 46), Mark Cullen.
For all the latest Luton Town FC news, reports, stats, player profiles, live match updates, MOM poll, prediction table and a complete fixture list, visit our Hatters Microsite.