1) Merlin (Merlin)
This guy can do almost everything! He has magic, a dragon (Aithusa) and knows how to cook from his time as King Arthur's servant and friend. Also he has a lot of life experience with overcoming adversary. When working with Gaius, he gains a lot of experience with healing both naturally and with magic. Definitely one for any team!
2) Bumblebee (Transformers)
He can fight, he has a great sense of humour and he never needs fuel. No ones likely to steal him as he would never let that happen. Very loyal, so would be a very beneficial team member. He can also be shelter for the others.
3) Erza Scarlet (Fairy Tail)
Powers: Requip: The Knight, Sword Magic, Telekinesis
Lightning Magic (while using Lightning Empress Armour)
Fire Magic (while using Flame Empress Armour)
Water Magic (while using Sea Empress Armour)
As I have listed Erza has the ability to switch weapons and armour in a instance which makes her very handy in combat. The armour can sometimes provide another use of magic with it, so her range is very wide. She is also very loyal to all who are considered family or friends. Ezra goes out of her way to destroy evil and save her friends making her very valuable to the team. She is also known for being very scary which is good for intimidating other groups. She is also very good at being in charge.