Hi Marcelo!
As a consultant BA, my answer might be atypical in some parts.
1. Multi-faceted issue:
a) for internal management you need to forecast usage of individual, business forecasts etc; do sales, hr management and development; do reporting; participate or lead project planning
b) for projects you'll have to do some or all of the 7 key areas of BABOK and related tasks. Also you usually get involved into project management at some degree. If you are following clients methodologies or practices instead of your own, it will get even more complicated.
2. Typical set in small assignments is excel, word, powerpoint and visio. I always use some kind of mind-mapping tool.
Various excel spreadsheets for budgeting, forecasting, reporting, analysis tasks etc.
powerpoint and visio for various models, presentations and visualisations
word for notes, memos, etc.
Mindmap sw is nice as it simultaneously allows you to create models of a kind and document things in textual format. They also usually allow you to export part or all of your map into word, powerpoint or as xml for further use maintaining hierarchical structure.
In larger assignments usually some requirements management tools such requisite pro, rcc or similar. Also uml or archimate compliant modeling tools as well as bpmn modeling tools.
IMO, problem is that there is lack of tools that would follow the real-life and BA mental model with multiple levels of details but remain fast and easy to use. Notepad is fast to type, but it doesn't create structures and relationships. Modeling tools do that, but they are slow to use in facilitated workshops or during interviews. Therefore you USUALLY end up with lots post-meeting /-workshop documentation work. Tool that would allow raw notes capture and refinement into chunks and then into finer-detailed models and document generation would be highly valuable. Kinda like architectural CAD applications. You can start by scanned pencil sketch and then add layers of details all the to HVAC plans and simulations of structural integrity and realistic walk-throughs.
I'm not sure if this the kind of inforamation you were looking for, but hope it helps
Petteri Miinalainen