I am thinking of something that would require extreme use of algorithms, maybe a search engine or a distributed computing systems.

Any other idea for heavily algorithim based project that would of course increase my marketability ? and by the way i have 2 instead of 1 year to complete the project if i start now.

Develop something in AI field? It is really heavy in algorithm, maths, and statistics. The future of this field is quite well.

and what about search engines are they complex ?

Depends on the data structure you are building and what input you are taking in for the search. It is straight forward. The only difficult part is how to do the index of data and create a data structure in order to optimize the search part.