Transmutation

Bob Bishop (Heroes)
Bob has the ability to change the composition of objects. According to a blurb about him on the assignment tracker map, Bob can turn objects only into gold. The amount of mass he can affect at one time is unknown, though he has turned an adult male named Hampton Connolly entirely into gold. After transmutation, Hampton Connolly was carried out by four men on a stretcher, suggesting his weight may not have significantly increased. However, it is not known whether only a shell of Hampton's form was left after transformation or whether the gold Hampton was transformed into weighed less than standard gold.

It is not yet known if there are materials Bob cannot transform. So far he has only used it to transform solids, it is unknown if it is possible to affect liquids or gases with this ability.

Since Bob's power does not automatically affect anything he touches, it must require some concentration to use.

Bob can apparently generate substantial quantities of gold over time, because he implies that his power is a significant source of the Company's funding.

Sylar (Heroes)
Utilizing control nearly equal to Bob's, Sylar was able to turn a gun to pure gold in a matter of seconds, only minutes after acquiring this ability.

Thomas Jones (Marvel)
Thomas has the ability to alter the chemical composition of anything he touches into its elemental components. He can also change matter into other forms so long as he fully understands the physical composition of the desired result. In his first appearance, he could only change objects into simple chemical elements, usually gold. Due to his study of biochemistry, he can now also change objects into more complex molecules, allowing him to change transmuted living beings back to normal.