For diversity sake, in no particular plague fits, you may choose a combination or make up your own. The First Plague (Exodus 7:14-24)
All of the water in Egypt - right from water already in buckets and jars, to ponds, canals, streams, even the Nile River - turned to blood. Then all of the fish of the river died, causing a terrible stench.
The Second Plague (Exodus 8:1-15)
Frogs miraculously multiplied in number, so many that the land was infested with the normally aquatic creatures. Even people's houses had them inside.
The Third Plague (Exodus 8:16-19)
Vast swarms of gnats tormented people and animals.
The Fourth Plague (Exodus 8:20-32)
Vast swarms of flies through the land, spreading disease.
The Fifth Plague (Exodus 9:1-7)
Disease on the livestock - horses, donkeys, camels, cattle, sheep and goats - but those of the Israelites were unharmed.
The Sixth Plague (Exodus 9:8-12)
Festering boils on people and animals through the land.
The Seventh Plague (Exodus 9:13-35)
Powerful hail storms that destroyed the standing crops. The hail stones were so big that any people or animals caught outside in the storm were killed.
The Eighth Plague (Exodus 10:1-20)
Locusts in such great numbers that the ground was covered with them. They devoured everything that survived the hail storm.
The Ninth Plague (Exodus 10:21-29)
Darkness over the entire land for three days - but the Israelites had light in Goshen.
The Tenth Plague (Exodus 11:1-10, 12:1-42)
Death of the firstborn. The Passover. Pharaoh let the Israelites go. The Wilderness Journey began.