TiCl4 is a strong Lewis acid but easily reducible to TiCl3.
Zn powder is an effective reducing agent.
Mg powder or chips can easily form organometallic compounds via an intermediate, free radical step.
1). Study carefully the mechanisms of McMurry coupling, Pinacol coupling and Clemmensen reduction and see what is the role of the above metals, therein.
2). Search for alternative metals and/or their salts that have similar properties with Zn and TiCl4 and which could replace them (say Sn and ZrCl4, respectively?).
Hint: Firstly, check their neighbors in the periodic table, before searching for more exotic metals like lanthanides and actinides.