Sa'Mac ("Desert" in Vietnamese; was searching for best name) is sand themed champion. My idea was to create tank, great support and initiator, but without strong damage skills, to make him balanced, not overpowered. He's melee. So let me introduce his skills:

Sand Skin (Passive) - Sa'Mac gains 5/10/15% Damage Reduction (changes on level 7 & 13).

I can't tell this passive is very strong. Kassadin starts with 15% magic damage reduction on 1st lv. This passive is just to help with building him as tank.

[Q Skill] Sand Bite (on-hit) - Sa'Mac gains additional 150/175/200/225/250 attack range for his next basic attack. Striking enemy slow his movement speed by 20/25/30/35/40% for 2 seconds and deal bonus 30/65/100/135/170 (+0.35 ablity power) magic damage. Lasts 8 seconds. Cooldown: 8/7/6/5/4 seconds. Mana cost: 20/26/32/38/44 mana.

His next basic attack creates sand pillar on enemy, dealing magic damage and slowing him. Great skill to chase enemy or last hit him from range. It's good to buy Trinity Force to make it stronger.

[W Skill] Desert Wind (active) - Create aura that raise nearby allied champions movement speed by 10/13/16/19/22% for 6 seconds. Cooldown: 16 seconds. Mana Cost: 60/70/80/90/100 mana. Range: 800

Another skill for chasing/running from enemies. Visually there's wind around Sa'Mac. Everybody in range get's the buff even if they enter after casting this skill.

[E Skill] Sand Shield (active) - Sa'Mac shields allied champion for 6 seconds, giving him bonus 10/20/30/40/50 Armor & Magic Restistance and 6/12/18/24/30% chance to slow attacker's movement and attack speed by 8/16/24/32/40% for 2.5 seconds. Cooldown: 15 seconds. Mana Cost: 80/90/100/110/120 mana. Range: 650.

This skill combined with Randuin's Omen gives you 50% chance to slow attacker's speed. Really helpful skill. Visually there's sand flying around marked champion.

[R Skill] Sandstorm (active) - Sa'Mac marks area (650 range; visible for enemies). After 1.5 second delay, he creates sandstorm in marked area. Every enemy champion and minion in area is slowed by 25/35/45% and blinded. After leaving area this effect last for additional 1 second. Sandstorm lasts for 7 seconds. Cooldown: 120/105/90 seconds. Mana Cost: 150 mana. Range to center AoE: 1000/1500/2000.

This skill just destroys any gank. It disables fighters, causing them to use their skills. It's easy to run from Sandstorm by enemy because of it's 1.5 second delay, but you can use it to protect turrets or yourself.

Build: I would go Ninja/Mercury Boots, then pure tanky items (eventually Trinity Force for Q skill). I can even suggest to buy Manamune because of his mana costs.

Epilogue: Sa'Mac is really great initiator. Placing ult from bush, then Q slow, then W bonus movement speed... Ah, with his skills you can tank every fighter. His weakness is probably Magic Resistance. He's great vs fighter but any mage can just defeat him. His counterpick is probably Kog'Maw. Sa'Mac have only 1 damaging skill, he can't be very powerful in 1 vs 1.

Waiting for your opinions ;) Thanks!