To my experience:
1. Everything that is common for all other cars (brakes - disks + pads + fluid), oil (use the recommended one ot better), HVAC (filter, cleaning), etc.
2. Drainage opening at the well where the top's hydraulic pump is located - those are VERY VERY VERY poorly designed. The pump (actually motor + pump) is incapsulated in a casing which is not sealed. The whole thing is placed in a well just in front of the rear left wheel and water (rain, snow, washing, etc.) has access to it. In theory, the drainage opening should let the water flow out. In practice this opening gets blocked very easilly by dirt and the pump ends up killed by corrosion (own experience). So periodical cleaning of this opening (I have seen excellent DIYs on the topic) will save $$$$.
3. The lights - mine are bixenon and both died due to moisture intake. The way those lights are designed is a pure joke, I can't believe Germans could do such a pathetic job. Halogen lights are way less sensitive to moisture intake but neverhteless not 100% resistant. Observe any traces of condensate in the lights and let them dry immediately by removing the lids at the back of the lights.