Formal:
* Reliable: This is a very common synonym and is often used interchangeably with "dependable."
* Trustworthy: Implies that the person or thing is worthy of trust and confidence.
* Faithful: Suggests a strong sense of loyalty and commitment.
* Consistent: Emphasizes that the person or thing performs or behaves in a predictable way.
Informal:
* Solid: Suggests strength and stability.
* Stable: Implies that the person or thing is not likely to change or fail.
* Count on: This is a phrase that means the same as "dependable."
* Always there: This implies that the person or thing is always available when needed.
The best synonym to use will depend on the specific situation and the desired tone.