Ganesha Pancharathnam by Adi Sankara

One of the first few slokas or bhajans taught in most schools. 

Mudakaraatha Modakam Sada Vimukti Saadhakam
Kalaadharaavatamsakam Vilasiloka Rakshakam
Anaaya Kaika Naayakam Vinasitebha Daityakam
Nataasubhasu Naashakam Namaami Tham Vinaayakam.

Natetaraati Bheekaram Navoditaarka Bhaasvaram
Namat Suraari Nirjanam Nataadhi Kaapa Duddharam
Suresvaram Nidheesvaram Gajesvaram Ganeshvaram
Mahesvaram Samaasraye Paraatparam Nirantaram.

Samasta Loka Samkaram Nirasta Daitya Kunjaram
Daredarodaram Varam Vare Bhavaktra Maksharam
Krupaakaram Kshamaakaram Mudaakaram Yasaskaram
Manaskaram Namaskrutaam Namaskaromi Bhaasvaram.

Akimchanaarti Marjanam Chirantanokti Bhaajanam
Puraari Poorva Nandanam Suraari Garva Charvanam
Prapancha Naasha Bheeshanam Dhananjayaadi Bhushanam
Kapola Daana Vaaranam Bhajaey Puraana Vaaranam.

Nitaantikaanta Dantakaanti Mantakaanta Kaatmajam
Achintya Rupa Mantaheena Mantaraaya Krintanam
Hrudantarey Nirantaram Vasantameva Yoginam
Tameka Danta Meva Tam Vichintayaami Santatam.

Phalasruthi

Maha Ganesa Pancha Rathna Maadharena Yo Anvaham,
Prajalpathi Prabhathake Hrudhi Smaran Ganeswaram,
Arogadhamadhosadham Susahitheem Suputhratham,
Samahithayurshta Bhoothi Mapyupaithi Sochiraath.