The scripts:
QFireTone
Plays a sound when you smoke someone (ka-ching!). Great for complex dogfights because you hear the kill before you would have normally even realized you took the guy out.
Also plays a 'be careful' message when you injure (or kill !) a teammate. Requires PJSupport1.cs.

QGunCam
Toggles on/off with alt-g. When activated, records a screenshot as soon as you kill someone. It imprints the screenshot with the victim's name for later reference. Might not sound like much, but it makes for fantastic action shots, especially nice for recording those long-range MA's and proving you did it :) I like to kill someone then send them the photo over icq as a memento. It's nor recommended for use during matches because of the time Tribes takes to record a screenshot, it will lag for up to a second. Requires PJSupport1.cs.

QSpeedHud
Displays a hud on the right edge of your screen that displays your current speed in meters/second. I like to use it when testing out ski routes.
Displays your current altitude and monitors your rate of ascent/descent so if you drop too fast the hud display changes from green to yellow to red and plays a subtle warning sound. The altitude displayed is not vs 'sea level' but is vs the ground directly under you.

QFPSHud
No surprise here, it displays your current FPS in a small hud docked to the left edge of your screen. The display changes color green/yellow/red if your framerate dips too much.

QPingHud
Politely positions itself just under the QFPSHud. The display changes color green/yellow/red if your ping dips too much. In testing, it does not appear to cause any network latency. Unlike the pinghuds in T1, this is actually accurate and consistent with the ping displayed in the player menu.

QPLHud
Politely positions itself just under the QPingHud. Displays your packet loss or 'PL'.
Optionally displays a bottomprint alert if a teammate's ping or PL puts him out of the game. Team commanders no longer have to wait until someone notices that so-and-so is just standing there before making team adjustments.

QRoger
Binds your 'r' key to say 'Roger.' to your team. Easily reconfigured to a different key. Does not yet have audio (ICQ me 13368969 if you know how to add it to a TeamMessageSent cmd.)
Can easily be changed to say other things - just change the text to your liking.

QRepairKit
Auto-uses any repair kits that you pick up from corpses... if you're not already at full health.

QDance
Makes your little Tribes dude dance a little Tribes jig... continuously. Find yourself a partner and go cut a rug.