To be fair, the machine gun with the bouncing alt-fire grenade isn't exactly a mindblower. A whole whack of mods had the same thing, actually (like the MechArm in NeoCairo). UT's grenade bounced, people wanted an assault rifle with an underslung grenade, so they put in the bouncy grenade onto a hitscan weapon. But yeah, 2k3 ripped off millions of mods to make the game.
To start, Bomb Run. That's BoomBall (you're playing a sport with a bomb) and FragBall (the ball launcher weapon) mixed to one.
Next, the Shield Gun (A carbon copy of the RDU in WFUT). Air jump and wall jump are from Matrix Moves. And last but not least, yes, the skeleton thing from U4e. I'm sure you can find someone with something like the Ion Cannon (like the mortar system in TFUT). The jeep is carbon copy from Halo. Zooming Instagib is - well, Zoom Instagib for UT.
Any number of mods had the adrenaline system - though I'll admit few of them handled the powers with button comboes like that.