From the other thread linked to:
Solar #3 (1991, first Toyo Harada)
Harbinger #1 with coupon (1992, first Harbinger team kids)
X-O Manowar #1 (1992, first X-O Manowar)
X-O Manowar #4 (1992, brief first Shadowman)
Shadowman #1 (1992, first full Shadowman)
Solar #10 (first printing, 1992, first Eternal Warrior, first Geomancers)
Archer & Armstrong #0 (1992, first Archer & Armstrong, but a limited gold variant exists)
Eternal Warrior #4 (1992, brief first Bloodshot)
Rai #0 (1992, first full Bloodshot, HARDCorps, key storylines issue)
Shadowman #8 (1992, first Master Darque)
Archer & Armstrong #8 (1992, first Ivar the Timewalker)
Solar #10 (second printing, 1992, first Eternal Warrior, first Geomancers)
Bloodshot #6 (1993, first Ninjak)
Shadowman #16 (1993, first Dr. Mirage)
Quantum & Woody #1 (1997 Acclaim title, first Quantum & Woody, two covers exist)
Many of these are technically "Modern" but they're all from the '90s.
I'd add Harbinger #15 (first Livewire) as well.