The Overhealer can boost a player's health to 200% of their maximum, and unlike the default Medi Gun's 150% overheal, this boost will not decay over time. The trade-off is that the Overhealer's ÜberCharge was to fill very slowly or possibly not at all.
The Overhealer would have been available to Medics after attaining a certain number of achievements, its eventual replacement being the Kritzkrieg. The model and materials for the Kritzkrieg attachment bear the filename
- http://pc.ign.com/articles/847/847435p1.html Valve Planning More Team Fortress Content article which mentioned the Overhealer, from IGN
- http://www.gamefront.com/overhealer-not-coming-to-team-fortress-2-after-all/ Overhealer Not Coming to Team Fortress 2 After All article, from GameFront