Where is it?
PLenty of them! Zombie, Gumbo, Calle 30, Buffalino, La Mucca, La Musa, Casa Federica, Nanai, Las noches de Moscú
Best gintonics and cocktails in the city! Cafeína, El 36, Picnic, Pez Gordo, Casa del Pez, El Tempo, Evaristo, La Realidad
La Musa, Faborit Coffee Shop, La Tape, Pepe Botella, Café de Mahón, Café Manuela
Most vanguard artistic shops are one step away. For clothes and all kind of accesories
Bit of culture
Malasaña is full of music and theater at night. A lot of venues have live music and theater shows: Teatro Alfil, Teatro Victoria, Teatro Lara, Microteatro. Concerts are in El Barco, El Tempo, Sala Taboo, Sala Sol, Sala Sirocco, etc...
Walks in the park
since you're right in the middle you can perfectly well walk to El Retiro, to Parque del Oeste, Jardines de Sabatini and Casa de Campo.
Spot of exercise
Tens of gyms within walking distance. Cycling is a major thing in this neighbourhood too.
I'm a mountaineer, so I'd go the Sierra in the North, la Pedriza or Peñalara, for a trekking. Historical cities like Segovia, Ávila, Sigüenza, Toledo, or Salamanca, which are one-two hours away, are really worth the visit.