Handy Mods to use in client

I've just been thinking, and since theres nothing in the mods section i've decided to start a new thread about Handy mods, i have already got 2 really handy mods, but if you know any good mods then please post on this thread

Handy Mods:
Rei's Minimap (A minimap)
Optifine (makes the game run smoother and in-game texture changing)

Flyro2000 wrote:
Rei's Minimap (A minimap)
Optifine (makes the game run smoother and in-game texture changing)

I use both of these.