tapUnlock is a new jailbreak tweak from the makers of MapsOpener and BrightVol. The tweak replaces the 'slide to unlock' bar with a 'tap to unlock' button. Personally I'm a fan of the classic slider, as it's part of how Apple introduced a new paradigm of capacitive screens to the mass market, and it's something I will always associate with the iPhone.
Unfortunately 'slide to unlock' isn't for everybody. If you know someone who has difficulty using the 'slide to unlock' gesture on the lock screen, maybe because of arthritis or another fine motor control difficulty, you'll get good mileage out of tapUnlock. Alternatively, you might just want it to have something different...